2021
56
Ja ie Pablo Na a o
De elopmen and op imiza ion o
3D ad anced unc ional magne ic
nanos uc u es g own by ocused
elec on beam induced deposi ion
Depa amen o
Di ec o /es
Física de la Ma e ia Condensada
De Te esa Nogue as, José Ma ía
Magén Domínguez, Césa
© Uni e sidad de Za agoza
Se icio de Publicaciones
ISSN 2254-7606
Ja ie Pablo Na a o
DEVELOPMENT AND OPTIMIZATION OF 3D
ADVANCED FUNCTIONAL MAGNETIC
NANOSTRUCTURES GROWN BY FOCUSED
ELECTRON BEAM INDUCED DEPOSITION
Di ec o /es
Física de la Ma e ia Condensada
De Te esa Nogue as, José Ma ía
Magén Domínguez, Césa
Tesis Doc o al
Au o
2020
Reposi o io de la Uni e sidad de Za agoza – Zaguan h p://zaguan.uniza .es
UNIVERSIDAD DE ZARAGOZA
Depa amen o de Física de la Ma e ia Condensada
Ins i u o de Nanociencia de A agón (INA)
Ins i u o de Ciencia de Ma e iales de A agón (ICMA)
Uni e sidad de Za agoza - Consejo Supe io de In es igaciones Cien í icas (CSIC)
Doc o al Thesis
De elopmen and op imiza ion o 3D ad anced
unc ional magne ic nanos uc u es g own by
ocused elec on beam induced deposi ion
________________________________________
Ja ie Pablo Na a o
Za agoza, Augus 2019
Thesis supe iso s:
José Ma ía de Te esa Nogue as
Césa Magén Domínguez

Con en s
Ag adecimien os (Acknowledgemen s) ........................................................................ 8
Ac onyms ...................................................................................................................... 11
Abs ac ......................................................................................................................... 13
Re e ences .............................................................................................................. 16
Resumen ........................................................................................................................ 17
Re e encias ............................................................................................................. 20
1 In oduc ion ............................................................................................................... 23
1.1 Nano echnology ................................................................................................ 24
1.2 Nanoelec onics ................................................................................................ 26
1.2.1 Non- ola ile esis i e memo y ............................................................... 28
1.3 Spin onics ........................................................................................................ 29
1.3.1 Magne ic domain walls .......................................................................... 30
1.3.2 Race ack memo y concep .................................................................... 31
1.4 Fu he applica ions o magne ic nanowi es ..................................................... 32
1.4.1 Spincalo i onics .................................................................................... 33
1.4.2 High equency de ices .......................................................................... 33
1.4.3 Biomedical applica ions ......................................................................... 34
1.4.4 Magne ic Fo ce Mic oscopy ips ............................................................ 35
1.4.5 Magne oplasmonics ............................................................................... 35
1.5 Design and ab ica ion o magne ic nanowi es ................................................. 36
1.5.1 Elec ochemical syn hesis ...................................................................... 36
1.5.2 Sol-gel echnique.................................................................................... 40
1.5.3 Vapo -liquid-solid and apo -solid p ocesses ........................................ 41
1.5.4 Chemical apo anspo me hod .......................................................... 42
1.5.5 Quenching and d awing echnique ......................................................... 44
1.5.6 Focused Elec on Beam Induced Deposi ion ......................................... 44
1.6 Ou line o he hesis .......................................................................................... 46
Re e ences ............................................................................................................... 47
2 Expe imen al echniques ........................................................................................... 57
2.1 Mic o- and nanoli hog aphy echniques ........................................................... 58
2.1.1 Dual Beam SEM-FIB sys em ................................................................. 58
2.1.1.1 Focused Elec on Beam Induced Deposi ion ............................... 64
2.1.2 Op ical li hog aphy................................................................................. 66
2.2 T ansmission Elec on Mic oscopy .................................................................. 68
2.2.1 T ansmission Elec on Mic oscopy echniques ...................................... 73
2.2.1.1 Elec on Ene gy Loss Spec oscopy ............................................ 74
2.2.1.2 Ene gy-Dispe si e X- ay Spec oscopy ...................................... 76
2.2.1.3 O -Axis Elec on Holog aphy .................................................... 77
2.3 Annealing echniques ........................................................................................ 82
2.4 Fu he magne ic cha ac e iza ion echniques .................................................. 83
2.4.1 Supe conduc ing Quan um In e e ence De ice magne ome y ............ 83
2.4.2 Magne o-Op ical Ke E ec magne ome y ......................................... 84
2.4.3 Magne ic Fo ce Mic oscopy .................................................................. 85
Re e ences ............................................................................................................... 87
3 Tuning he g ow h o 3D nanowi es by FEBID ...................................................... 95
3.1 P inciples o FEBID .......................................................................................... 96
3.2 Tailo ing he undamen al p ope ies o 3D cobal nanowi es ......................... 99
3.2.1 Expe imen al de ails ............................................................................. 101
3.2.2 Linea and adial g ow h egimes......................................................... 102
3.2.3 Composi ion as a unc ion o he g ow h egime ................................. 106
3.2.4 Magne ic induc ion as a unc ion o he diame e ................................ 112
3.2.5 Discussion o he esul s ...................................................................... 114
3.3 Elec ically-biased pa e ned me al s uc u e .................................................. 115
3.3.1 In oduc ion .......................................................................................... 116
3.3.2 Expe imen al de ails ............................................................................. 117
3.3.3 G ow h on insula ing subs a es ........................................................... 119
3.3.4 Elec ic ield nume ical calcula ions .................................................... 121
3.3.5 Dimensional modula ion as a unc ion o he applied ol age ............. 124
3.3.6 Quali a i e discussion o he elec ic ield ac ion ................................ 127
3.3.7 Dimensional modula ion as a unc ion o he beam de ocus ............... 129
3.4 Conclusions .................................................................................................... 136
Re e ences ............................................................................................................ 137
4 Towa ds p ope ies imp o emen by he mal annealing .................................... 145
4.1 In oduc ion .................................................................................................... 146
4.2 Annealing p ocess on 3D cobal nanowi es .................................................... 148
4.2.1 Expe imen al de ails ............................................................................. 149
4.2.2 S uc u al and chemical changes as a unc ion o he annealing
empe a u e .......................................................................................... 154
4.2.3 Magne ic induc ion dependence wi h annealing empe a u e .............. 162
4.2.4 Magne ic cha ac e iza ion by nanoSQUID magne ome y .................. 165
4.3 Annealing p ocess on 3D i on nanowi es ....................................................... 172
4.3.1 Expe imen al de ails ............................................................................. 172
4.3.1.1 In si u pos -g ow h annealing .................................................... 173
4.3.1.2 Ex si u pos -g ow h annealing ................................................... 174
4.3.2 Mo phology and composi ion o in si u annealed nanowi es .............. 176
4.3.3 Mo phology and composi ion o ex si u annealed nanowi es .............. 185
4.4 Conclusions .................................................................................................... 190
Re e ences ............................................................................................................ 191
12
HAADF: High-Angle Annula Da k Field
HCP: Hexagonal-Closes -Packed
HRTEM: High Resolu ion T ansmission Elec on Mic oscopy
IBE: Ion Beam E ching
ICE: Ion-Con e sion and Elec on
ICMA: Ins i u o de Ciencia de Ma e iales de A agón
ICMM: Ins i u o de Ciencia de Ma e iales de Mad id
ICT: In o ma ion and Communica ions Technology
INA: Ins i u o de Nanociencia de A agón
IP: In-Plane
LACBED: La ge Angle Con e gen Beam Elec on Di ac ion
LMA: Labo a o io de Mic oscopías A anzadas
LMI: Liquid Me al Ion
MEMS: Mic o-Elec o-Mechanical Sys ems
MFM: Magne ic Fo ce Mic oscopy
MOKE: Magne o-Op ical Ke E ec
MRAM: Magne o esis i e Random-Access Memo y
MTJ: Magne ic Tunnel Junc ion
OOMMF: Objec O ien ed Mic oMagne ic F amewo k
OOP: Ou -O -Plane
PEEM: Pho oEmission Elec on Mic oscopy
ReRAM: Resis i e Random-Access Memo y
SAED: Selec i e A ea Elec on Di ac ion
SE: Seconda y Elec ons
SEM: Scanning Elec on Mic oscopy
S-FEG: Scho ky Field Emission Gun
SQUID: Supe conduc ing Quan um In e e ence De ice
STEM: Scanning T ansmission Elec on Mic oscopy
STO: S on ium Ti anium Oxide
TEM: T ansmission Elec on Mic oscopy
TLD: Th ough Lens De ec o
TMR: Tunnel Magne o esis ance
UV: Ul a iole
VLS: Vapo -Liquid-Solid
VS: Vapo -Solid
XMCD: X- ay Magne ic Ci cula Dich oism
YBCO: Y ium Ba ium Coppe Oxide

13
Abs ac
Magne ic nanos uc u ed ma e ials a ac pa icula ly keen in e es because o hei
possibili ies o be implemen ed in u u e spin onic de ices [1]. Speci ically,
e omagne ic nanowi es and nano ubes a e po en ial candida es o as and low-powe
domain wall condui used o s o ing and handling in o ma ion. In his ega d, one o he
mos e sa ile and p omising echniques o he ab ica ion o hese nanos uc u es is
Focused Elec on Beam Induced Deposi ion (FEBID) [2]. As has been cus oma y o
mo e han 35 yea s, mainly wo-dimensional (2D) deposi s ha e been ab ica ed by his
me hod. Howe e , o mee he new ma ke equi emen s o he de elopmen o mo e
ene gy-e icien de ices, ad anced h ee-dimensional (3D) magne ic nano-objec s
eme ge as ex ao dina ily p omising s uc u es o applica ions in magne ic da a s o age,
logic and sensing.
This documen includes di e en app oaches o he uning o dimensional,
composi ional and magne ic p ope ies o 3D e omagne ic nanowi es. In his con ex ,
he new ARchi ec u al Adjus men by G id O e lay Nano echnology (ARAGON) Chip
ep esen s a s ep o wa d in he ab ica ion o ailo ed unc ional nanowi es by FEBID
on insula ing subs a es, which had been una ainable due o he impossible cha ge
dissipa ion. This consis s o an elec ically-biased pa e ned me al s uc u e which allows
he g ow h and he in si u modula ion o he nanowi e geome y.
Al hough many e o s ha e been ca ied ou o imp o e he p ope ies o 2D
deposi s [3], sca ce in es iga ions ha e been pe o med in 3D nanos uc u es. In his
ligh , he nano ab ica ion o 3D Co and Fe nanowi es by FEBID and he subsequen ex
si u and in si u pos -g ow h annealing ea men s ha e been explo ed o he i s ime
[4][5]. High Resolu ion T ansmission Elec on Mic oscopy (HRTEM) imaging, Elec on
Ene gy Loss Spec oscopy (EELS) in Scanning T ansmission Elec on Mic oscopy
(STEM) mode and Elec on Holog aphy (EH) ha e been used o moni o he s uc u al,
14
chemical and magne ic al e a ions a each annealing empe a u e. The me allic
composi ion inc eases wi h he empe a u e up o ~95% a ., a ec ys alliza ion o he
s anda d nanoc ys alline as-deposi ed s uc u e in o la ge monoc ys als, whose size is
compa able o he nanowi e diame e , is p oduced and he a e age ne magne ic induc ion
inc eases d ama ically o alues e y close o he bulk one. This achie emen opens new
pa hs o he ab ica ion o ei he indi idual o a ays o 3D nanowi es wi h high pu i y
and c ys allini y based on o he ma e ials, ob aining nanos uc u es which could be used
o u u e applica ions.
On he o he hand, he combina ion o mo e han one ma e ial by FEBID can gi e
ise o new unc ionali ies. On his basis, nanoscale he e os uc u ed ma e ials in he o m
o 3D co e-shell nanowi es ha e been de eloped [6]. This new app oach has been applied
o syn hesize s anding nanowi es wi h e omagne ic co es o Co o Fe coa ed wi h a
p o ec i e P -C shell. This a chi ec u e aims a minimizing he deg ada ion o magne ic
p ope ies caused by he na u al su ace oxida ion o he co e o a non- e omagne ic
ma e ial. This is a key issue in such hin e omagne ic objec s wi h a high su ace- o-
olume a io. The s uc u e and chemis y o he nanowi es ha e been cha ac e ized in
P -C-coa ed and uncoa ed nanos uc u es, e ealing ha he su ace oxida ion is
supp essed om he magne ic co es and con ined o he P -C laye , while keeping he
cylind ical shape. The magne ic cha ac e iza ion has demons a ed ha he a e age
magne iza ion o he coa ed co es is s eng hened up o 30% in he hinnes nanowi es
(~40-nm- hick co es) wi h espec o he unp o ec ed ones.
Based on he me hod de eloped o g ow 3D co e-shell nanos uc u es by his
ab ica ion echnology, he g ow h and cha ac e iza ion o 3D e omagne ic Co
nano ubes ha e been pe o med. The he e os uc u ed ma e ials a e composed by a 3D
P -C nanowi e ac ing as a co e, and a Co coa ing o ming he shell and he nano ube
a chi ec u e. TEM expe imen s on a c oss sec ion ha e shown co es hinne han 100 nm
and shells down o ~11 nm in hickness. The magne ic cha ac e iza ion pe o med by EH
15
and Magne o-Op ical Ke E ec (MOKE) magne ome y demons a es hei
e omagne ic beha iou , and mic omagne ic simula ions we e ca ied ou o unde s and
he domain wall dynamics. These esul s p o e ha hese nanos uc u es p o ide g ea
unc ionali y wi h po en ial applica ion in he pe o mance o magne ic de ices.
In he pas , a di ec use o FEBID was he g ow h o magne ic ips o wid h a ound
50 nm wi h po en ial applica ion in Magne ic Fo ce Mic oscopy (MFM) [7]. In o de o
show ha FEBID ips a e supe io han s anda d MFM ips and can lead o he nex -
gene a ion o comme cial MFM ips, dedica ed expe imen s o he g ow h o e ical Co
and Fe nanowi es ha e been ca ied ou . He e, he op imiza ion o he MFM ips g own
by FEBID and a compa ison o hei beha iou o ha o s anda d MFM ips ha e been
assessed. The ips ha e been es ed in MFM expe imen s, in ambien condi ions as well
as in liquid en i onmen , beha ing app op ia ely in e ms o mechanical s abili y,
esolu ion and sensi i i y [8]. Indeed, i has been demons a ed ha Fe ips wi h 34 nm in
diame e and a 7 nm-wide sha p end can be ab ica ed o achie e e y high esolu ion as
well as ela i ely low sample- ip magne ic in e ac ion o minimize he in luence o he
magne ic ip on he magne ic s a e o small s uc u es such as sky mions. The Fe con en
is ound o dec ease as he ip end is app oached, which in luences he magne iza ion
alue and he magne ic s ay ields gene a ed a ound he ip end. This is he i s s ep
owa ds he esea ch on quan i a i e MFM measu emen s.
Finally, aking ad an age o he e sa ili y o he FEBID echnique, 3D P -C-coa ed
Co nanowi es wi h a shape-con olled s uc u e ha e also been ab ica ed. This
a chi ec u e consis s o o ming bends along he heigh (pinning si es), whe e domain
walls can be loca ed and ob ained a emanence a e sa u a ing he magne iza ion wi h
an applied magne ic ield in he app op ia e di ec ion [9]. The e o e, he g ow h o
complex a chi ec u es by FEBID opens new p ospec s o he de elopmen o no el
magne ic de ices.
16
Re e ences
[1] A. Fe nández-Pacheco, L. Se ano-Ramón, J. M. Michalik, M. R. Iba a, J. M. De
Te esa, L. O’B ien, D. Pe i , J. Lee and R. P. Cowbu n, “Th ee dimensional
magne ic nanowi es g own by ocused elec on-beam induced deposi ion”, Sci.
Rep. 3, 1492 (2013).
[2] J. Pablo-Na a o, D. Sanz-He nández, C. Magén, A. Fe nández-Pacheco and J.
M. De Te esa, “Tuning shape, composi ion and magne iza ion o 3D cobal
nanowi es g own by ocused elec on beam induced deposi ion (FEBID)”, J.
Phys. D: Appl. Phys. 50, 18LT01 (2017).
[3] M. V. Puydinge dos San os, M. F. Velo, R. D. Domingos, Y. Zhang, X. Maede ,
C. Gue a-Nuñez, J. P. Bes , F. Bé on, K. R. Pi o a, S. Moshkale , J. A. Diniz and
I. U ke, “Annealing-Based Elec ical Tuning o Cobal -Ca bon Deposi s G own
by Focused Elec on-Beam-Induced Deposi ion”, ACS Appl. Ma e . In e aces 8,
32496 (2016).
[4] J. Pablo-Na a o, C. Magén and J. M. De Te esa, “Pu i ied and C ys alline Th ee-
Dimensional Elec on-Beam-Induced Deposi s: The Success ul Case o Cobal
o High-Pe o mance Magne ic Nanowi es”, ACS Appl. Nano Ma e . 1, 38
(2018).
[5] J. Pablo-Na a o, R. Winkle , G. Habe ehlne , C. Magén, H. Plank and J. M. De
Te esa, “In si u eal ime annealing o ul a hin e ical Fe nanowi es g own by
ocused elec on beam induced deposi ion”, Ac a Ma e ialia 174, 379 (2019).
[6] J. Pablo-Na a o, C. Magén and J. M. De Te esa, “Th ee-dimensional co e-shell
e omagne ic nanowi es g own by ocused elec on beam induced deposi ion”,
Nano echnology 27, 285302 (2016).
[7] M. Ga agnin, H. D. Wanzenboeck, S. Wach e , M. M. Shaw a , A. Pe sson, K.
Gunna sson, P. S edlindh, M. S öge -Pollach and E. Be agnolli, “F ee-S anding
Magne ic Nanopilla s o 3D Nanomagne Logic”, ACS Appl. Ma e . In e aces
6, 20254 (2014).
[8] M. Jaa a , J. M. De Te esa, A. Asenjo, J. Pablo-Na a o, P. A es, C. Magén and
J. Gómez-He e o, “Sys em o an A omic Fo ce Mic oscope”. Spanish OEPM
P201731292 (2017) and In e na ional pa en PCT/ES2018/070709 (2018).
[9] A. Wa elle, J. Pablo-Na a o, M. S aňo, S. Bochmann, S. Pai is, M. Rioul , C.
Thi ion, R. Belkhou, J. M. De Te esa, C. Magén and O. F ucha , “T ansmission
XMCD-PEEM imaging o an enginee ed e ical FEBID cobal nanowi e wi h a
domain wall”, Nano echnology 29, 045704 (2018).
17
Resumen
Los ma e iales magné icos nanoes uc u ados a aen un in e és pa icula debido a
la posibilidad de se implemen ados en u u os disposi i os espin ónicos [1].
Especí icamen e, los nanohilos y nano ubos e omagné icos son candida os po enciales
pa a se u ilizados como ehículos excelen es pa a las pa edes de dominio, usadas pa a
almacenamien o y p ocesamien o de in o mación. En es e sen ido, una de las écnicas
más e sá iles y p ome edo as pa a la ab icación de es as nanoes uc u as es la
deposición inducida po haz de elec ones ocalizado (FEBID) [2]. Como iene siendo
habi ual desde hace más de 35 años, median e es a écnica se han ab icado
undamen almen e depósi os en dos dimensiones (2D). Sin emba go, pa a da espues a
a las exigencias del me cado ac ual con elación al desa ollo de disposi i os más
e icien es ene gé icamen e, los nano-obje os magné icos a anzados en es dimensiones
(3D) se e igen como es uc u as sumamen e p ome edo as pa a aplicaciones en
almacenamien o, de ección y lógica magné icos.
Es a esis incluye di e en es es a egias pa a con ola las p opiedades
dimensionales, composicionales y magné icas de nanohilos 3D e omagné icos. En es e
con ex o, un nue o mé odo cimen ado en un chip nano ecnológico basado en una
cuad ícula supe pues a pa a modi icaciones es uc u ales (ARAGON) ep esen a un paso
adelan e en la ab icación de nanohilos uncionales diseñados po FEBID sob e sus a os
aislan es, lo cual había sido inalcanzable debido a la imposibilidad de la disipación de
ca ga eléc ica du an e el c ecimien o. Es a es a egia consis e en una es uc u a me álica
some ida a una di e encia de po encial que pe mi e la ab icación y la modulación in si u
de la geome ía del nanohilo.
A pesa de que se han lle ado a cabo muchos es ue zos pa a mejo a las p opiedades
de los depósi os 2D [3], escasas in es igaciones se han ealizado con elación a las
nanoes uc u as 3D. Desde es e pun o de is a, se ha explo ado po p ime a ez la

18
nano ab icación de nanohilos 3D de Co y Fe c ecidos po FEBID y los pos e io es
a amien os é micos ex si u e in si u [4][5]. Pa a moni o iza los cambios es uc u ales,
químicos y magné icos en cada empe a u a, se ha u ilizado mic oscopía elec ónica de
ansmisión de al a esolución (HRTEM), espec oscopía po pé dida de ene gía de los
elec ones (EELS) usando el modo de mic oscopía elec ónica de ansmisión po ba ido
(STEM), y holog a ía elec ónica (EH). En pa icula , la composición me álica
inc emen a con la empe a u a has a ~95% a ., se p oduce la ec is alización de la
es uc u a nanoc is alina inicial en g andes monoc is ales cuyo amaño es compa able al
diáme o del nanohilo, y la inducción magné ica media ne a aumen a signi ica i amen e
has a alo es muy p óximos al del ma e ial masi o. Es os esul ados ab en nue os
caminos hacia la ab icación de nanohilos 3D indi iduales o en se ie, con g an pu eza y
c is alinidad, basados en o o ipo de ma e iales, ob eniendo nanoes uc u as que pod ían
se u ilizadas pa a u u as aplicaciones.
Po o o lado, la combinación de más de un ma e ial po FEBID puede da luga a
nue as uncionalidades. Po ello, se han desa ollado ma e iales he e oes uc u ados en
o ma de nanohilos 3D con un núcleo y un ecub imien o [6]. Es a nue a es a egia ha
sido aplicada pa a sin e iza nanohilos e icales con núcleos e omagné icos de Co o Fe
ecubie os de una capa p o ec o a de P -C. Es a a qui ec u a iene como obje i o
minimiza la deg adación de las p opiedades magné icas debido a la oxidación supe icial
na u al del núcleo, con i iendo es a capa ex e na en un ma e ial no e omagné ico. Es o
es una cues ión cla e en obje os e omagné icos es echos con un cocien e
supe icie/ olumen al o. Las p opiedades es uc u ales y químicas de los nanohilos han
sido ca ac e izadas en nanoes uc u as sin ecub i y ecubie as con P -C, mos ando que
la oxidación supe icial se sup ime de los núcleos magné icos y es con inada en la capa
de P -C, al mismo iempo que se conse a su o ma cilínd ica. La ca ac e ización
magné ica ha demos ado que la inducción magné ica media de los nanohilos ecubie os
19
aumen a has a un 30% en el caso de los nanohilos más es echos (diáme os de ~40 nm)
con espec o a los núcleos sin ecub i .
Basándonos en es e mé odo pa a el c ecimien o de nanoes uc u as 3D con un núcleo
y un ecub imien o median e es a ecnología de ab icación, se ha lle ado a cabo la
sín esis y ca ac e ización de nano ubos e omagné icos 3D de Co. En es e caso, la
he e oes uc u a es á compues o po un nanohilo 3D de P -C ac uando como núcleo, y un
e es imien o de Co o mando el ecub imien o y la a qui ec u a del nano ubo. Los
expe imen os de TEM sob e una sección ans e sal muy delgada han mos ado núcleos
con diáme os meno es de 100 nm y ecub imien os que se educen has a ~11 nm de
espeso . La ca ac e ización magné ica ealizada median e EH y magne ome ía de e ec o
Ke magne o-óp ico (MOKE) demues a su compo amien o e omagné ico. Asimismo,
se han lle ado a cabo simulaciones mic omagné icas pa a comp ende la dinámica de las
pa edes de dominio. Es os esul ados p ueban que es as nanoes uc u as o ecen g an
uncionalidad con po enciales aplicaciones en disposi i os magné icos.
En el pasado, un uso di ec o de la écnica FEBID consis ía en el c ecimien o de
pun as magné icas con diáme os de al ededo de 50 nm con posibles aplicaciones en
mic oscopía de ue za magné ica (MFM) [7]. Pa a demos a que las pun as c ecidas po
FEBID son supe io es a las pun as MFM es ánda , y que pueden da luga a la siguien e
gene ación de pun as MFM come ciales, se han ealizado expe imen os des inados al
c ecimien o de nanohilos e icales de Co y Fe. Se ha e aluado la op imización de las
pun as MFM c ecidas po FEBID y se ha ealizado una compa ación de su
compo amien o con espec o a las pun as MFM es ánda . Las pun as han sido analizadas
en expe imen os MFM, an o en condiciones ambien ales como en en o no líquido,
compo ándose ap opiadamen e en é minos de es abilidad mecánica, esolución y
sensibilidad [8]. Se ha demos ado que las pun as de Fe de 34 nm de diáme o con un
diáme o inal de 7 nm en el ex emo pueden se ab icadas pa a consegui an o al a
esolución como una in e acción magné ica mues a-pun a ela i amen e baja que
20
minimice la in luencia de la pun a magné ica sob e el es ado magné ico de es uc u as
pequeñas ales como sky miones. Además, se ha de ec ado que el con enido de Fe
dec ece cuando la dis ancia a la pun a se educe, lo cual iene e ec os sob e los alo es
de la inducción magné ica y los campos de uga gene ados en las p oximidades de la
pun a. Es e es el p ime paso hacia la in es igación des inada a medidas de MFM
cuan i a i o.
Finalmen e, ap o echando la e sa ilidad de la écnica FEBID, ambién se han
ab icado nanohilos 3D de Co ecubie os con P -C con una mo ología dis in a a la de
un pila . Es a a qui ec u a consis e en o ma cu a u as a lo la go de la longi ud del
nanohilo (si ios de anclaje), donde las pa edes de dominio pueden es a localizadas,
ob eniéndose después de sa u a la magne ización con un campo magné ico aplicado en
la di ección ap opiada [9]. Po lo an o, el c ecimien o de a qui ec u as 3D complejas po
FEBID ab e nue as pe spec i as pa a el desa ollo de no edosos disposi i os
magné icos.
Re e encias
[1] A. Fe nández-Pacheco, L. Se ano-Ramón, J. M. Michalik, M. R. Iba a, J. M. De
Te esa, L. O’B ien, D. Pe i , J. Lee and R. P. Cowbu n, “Th ee dimensional
magne ic nanowi es g own by ocused elec on-beam induced deposi ion”, Sci.
Rep. 3, 1492 (2013).
[2] J. Pablo-Na a o, D. Sanz-He nández, C. Magén, A. Fe nández-Pacheco and J.
M. De Te esa, “Tuning shape, composi ion and magne iza ion o 3D cobal
nanowi es g own by ocused elec on beam induced deposi ion (FEBID)”, J.
Phys. D: Appl. Phys. 50, 18LT01 (2017).
[3] M. V. Puydinge dos San os, M. F. Velo, R. D. Domingos, Y. Zhang, X. Maede ,
C. Gue a-Nuñez, J. P. Bes , F. Bé on, K. R. Pi o a, S. Moshkale , J. A. Diniz and
I. U ke, “Annealing-Based Elec ical Tuning o Cobal -Ca bon Deposi s G own
by Focused Elec on-Beam-Induced Deposi ion”, ACS Appl. Ma e . In e aces 8,
32496 (2016).
[4] J. Pablo-Na a o, C. Magén and J. M. De Te esa, “Pu i ied and C ys alline Th ee-
21
Dimensional Elec on-Beam-Induced Deposi s: The Success ul Case o Cobal
o High-Pe o mance Magne ic Nanowi es”, ACS Appl. Nano Ma e . 1, 38
(2018).
[5] J. Pablo-Na a o, R. Winkle , G. Habe ehlne , C. Magén, H. Plank and J. M. De
Te esa, “In si u eal ime annealing o ul a hin e ical Fe nanowi es g own by
ocused elec on beam induced deposi ion”, Ac a Ma e ialia 174, 379 (2019).
[6] J. Pablo-Na a o, C. Magén and J. M. De Te esa, “Th ee-dimensional co e-shell
e omagne ic nanowi es g own by ocused elec on beam induced deposi ion”,
Nano echnology 27, 285302 (2016).
[7] M. Ga agnin, H. D. Wanzenboeck, S. Wach e , M. M. Shaw a , A. Pe sson, K.
Gunna sson, P. S edlindh, M. S öge -Pollach and E. Be agnolli, “F ee-S anding
Magne ic Nanopilla s o 3D Nanomagne Logic”, ACS Appl. Ma e . In e aces
6, 20254 (2014).
[8] M. Jaa a , J. M. De Te esa, A. Asenjo, J. Pablo-Na a o, P. A es, C. Magén and
J. Gómez-He e o, “Sys em o an A omic Fo ce Mic oscope”. Spanish OEPM
P201731292 (2017) and In e na ional pa en PCT/ES2018/070709 (2018).
[9] A. Wa elle, J. Pablo-Na a o, M. S aňo, S. Bochmann, S. Pai is, M. Rioul , C.
Thi ion, R. Belkhou, J. M. De Te esa, C. Magén and O. F ucha , “T ansmission
XMCD-PEEM imaging o an enginee ed e ical FEBID cobal nanowi e wi h a
domain wall”, Nano echnology 29, 045704 (2018).
Chap e 1
28
In o e come hese impending limi a ions, he minia u iza ion enginee ing, which
has been leading he enhancemen o he chips pe o mance o he p esen , mus be d i en
by new s a egies and pa adigms [21]. One o he possibili ies is he “Mo e Moo e”
app oach, based on be e sys em designs using he same elec onic componen s. The
second one, ounded on he inco po a ion o new unc ionali ies and he expansion o 3D
a chi ec u es o cu en semiconduc o echnology, is called he “Mo e han Moo e”
s a egy. In his case, non-digi al and non-elec onic da a (op ical, mechanical, he mal,
e c.) a e combined wi h digi al in o ma ion in a single de ice, wi hou he need o
ollowing he adi ional scale educ ion pace o he digi al componen s. As a esul , hese
s a egic plans could b ing abou posi i e ad ances in nanoelec onics and lead o he
de elopmen o a b oad di e si y o applica ions [22].
1.2.1 Non- ola ile esis i e memo y
One o he bes examples in line wi h he a gumen s se ou p e iously is he non-
ola ile esis i e memo y. Wi hin he sphe e o nanoelec onics, i should be highligh ed
ha he cu en lash memo y echnology is encoun e ing downscaling es ic ions, so
esea ch on he densi y and pe o mance inc ease o he non- ola ile memo ies s ands as
an u gen challenge o wo k in [23][24].
One possible al e na i e is he esis i e andom access memo y (ReRAM), aking
ad an age o a high-speed esis i e swi ching mechanism in me al/insula o /me al
s uc u es [25]. This sys em is cha ac e ized by ul a-small conduc ing ilamen s (~1-10
nm in diame e ), which appea in he oxide insula ing laye due o he elec ical
b eakdown phenomenon when an elec ic ield abo e a ce ain h eshold is applied
be ween he wo me al elec odes. Thus, hese ilamen s a e esponsible o modi ying
he anspo p ope ies o he capaci o a he nanoscale [26]. Since he wo k epo ed on
NiO nanowi es in 2008 [27], se e al expe imen s ha e been pe o med in o de o
imp o e he esis i e swi ching beha iou by inc easing he endu ance and s abili y [28]

In oduc ion
29
o educing he ope a ing ol age o he de ice [29]. In addi ion, no el app oaches ha e
been epo ed o he in eg a ion o hese nanowi es in o memo y de ices such as he
c ossba a ay me hodology including me al-oxide co e-shell nanowi e he e os uc u es
[30].
An imp essi e applica ion o hese nanowi es s ems om he possibili y o
ab ica ing lexible elec onic ci cui s, which can be po able and wea able. As a esul ,
he oxide nanowi es a e p omising candida es o be inco po a ed in elec onic de ices o
acking human heal h pa ame e s whe e he da a could be s o ed [31].
Figu e 1.3. Schema ic image o a con en ional esis i e memo y and a nanowi e one based
on a me al-oxide-me al he e os uc u e. A Scanning Elec on Mic oscopy (SEM) image o a
Au-NiO-Au nanowi e is shown o illus a e he eal sys em [32].
1.3 Spin onics
The manipula ion o he elec on spin as well as he elec on cha ge in solid s a e
sys ems is he undamen al basis o spin onics. In o de o unlock and ake ull ad an age
o his po en ial, he unde s anding o he in e play be ween he spin and i s en i onmen
becomes c ucial [33].
Encompassing he knowledge o igina ed om he combina ion be ween he spin-
dependen anspo phenomena and elec onics, se e al applica ions ha e been
de eloped [34]. In pa icula , he use o e omagne ic ma e ials, whe e he elec ical
esis ance depends on he elec on cu en spin pola iza ion, ha e gi en ise o ema kable
Chap e 1
30
miles ones. The i s g ea example is he concep o magne o esis i e ead head magne ic
eco ding in 1971, based on he aniso opy magne o esis ance (AMR) [35], and i s
comme cializa ion some yea s la e [36]. Addi ionally, he disco e y o he unnel
magne o esis ance (TMR) in 1975 b ough an unp eceden ed e olu ion, es ablishing he
basis o he non- ola ile magne o esis i e andom-access memo y (MRAM) [37].
Howe e , he inding o he gian magne o esis ance (GMR) in 1988 by A. Fe and P.
G ünbe g is conside ed as he main achie emen in his ield. This accomplishmen
dese es a special men ion because i ca apul ed spin onics and he p oduc ion o no el
ead heads o ha d disks d i es by IBM since 1997. The GMR e ec has u ned in o a
p ac ical and eal nanoscale de ice o widesp ead applica ions [38][39].
These b eak h oughs s imula ed new pe spec i es on he in e play be ween elec on
anspo and magne ic p ope ies, p omp ing he in es iga ion o no el e ec s emana ing
om he spin-cha ge cu en s in e ac ion, including swi ching mechanisms o he
magne ic momen s [40], such as he spin ans e o que phenomenon. Speci ically,
magne ic nanowi es a e ideal sca olds whe e many o hese phenomena can ake place.
1.3.1 Magne ic domain walls
Magne ic domain walls can be de ined as nano-objec s which sepa a e egions o
di e en magne iza ion o ien a ion, minimizing he magne os a ic ene gy. The balance
be ween his ene gy, he magne ic aniso opy and he exchange ene gy de e mines hei
o ma ion and na u e. The s udy o hese nanoscale ansi ion a eas as a ool o compu e
bina y in o ma ion in in eg a ed magne ic ci cui s is a majo s ep. Domain wall condui
can be achie ed by he applica ion o ex e nal magne ic ields o cu en s [41][42], and
he con ol o his p ocess in magne ic nanos uc u es, such as nanowi es, a ac s
pa icula ly keen in e es because o hei possible applica ion in s o age [43], memo y
[44] and logic de ices [45]. Especially, he high domain wall eloci ies p esen in ci cula
magne ic nanowi es, he po en ial supp ession o he Walke b eakdown phenomenon o
In oduc ion
31
he eme gence o new ypes o domain walls such as cu ling s a es o Bloch poin s a e
cha ac e is ics which make hem special a chi ec u es.
The capabili y o mo e magne ic domain walls in magne ic acks, e.g. nanowi es,
pa icula ly by spin ans e o que using spin-pola ized elec ical cu en s, opens new
ou looks conside ing he s o age ack memo y as he p omising candida e [46]. In his
case, he in o ma ion s o age uni ( he bi ) is he domain wall, a he han he magne ic
domain i sel in he con en ional ha d disks. The as p ocessing ime o he
semiconduc o in eg a ed ci cui s (CMOS) is conse ed wi h no mechanical mo emen
o he componen s. In addi ion, he con igu a ion o he domain wall sequence can be
e y e sa ile, p esen ing 2D s aigh , ben o loop shapes. The ul ima e geome y would
be 3D magne ic acks, as in oduced by S. S. P. Pa kin in 2008, which would de ini ely
boos he s o age a eal densi y o compe e wi h exis ing echnologies [44].
1.3.2 Race ack memo y concep
The concep o he ace ack memo y, ep esen ed in Figu e 1.4, is composed by a
magne ic ack wi h a sequence o domain walls and wo heads de o ed o w i ing and
eading da a. The w i e head can use di e en s a egies o gene a e a domain wall, such
as an Oe s ed line, o he magne ic unnel junc ion (MTJ) a chi ec u e as he ead head
does [47]. In his case, an insula ing ba ie sepa a es wo e omagne ic laye s whose
magne iza ion is ixed in one laye and changeable in he o he one [48]. This enables
wo di e en magne ic con igu a ions (pa allel o an ipa allel) wi h di e en unnel
esis ance, building he logic con igu a ion. In p ac ice, a spin-pola ized cu en induces
he domain wall mo ion along he magne ic s uc u e (shi ing), he w i e head swi ches
he magne iza ion locally, nuclea ing domain walls (w i ing) which ge pinned (s o ing)
and he ead head de ec s he magne iza ion di ec ion ( eading).
Chap e 1
32
Figu e 1.4. (a) Composi ion o he magne ic unnel junc ion wi h he wo possible
con igu a ions used in he w i e and ead heads. (b) Schema ic diag am o a ace ack memo y
concep [47].
The domain wall displacemen is ypically d i en by spin- ans e - o que as a esul
o he spin-pola ized cu en s injec ed in o he e omagne . In he las decade, wall
eloci ies up o 150 m/s using cu en densi ies abo e 100 MA/cm
2
ha e been eached
by a la e al cu en injec ion [49]. The speed was enhanced by in oducing a me allic
laye wi h s ong spin-o bi coupling unde he e omagne ic ack, bu keeping he high
cu en densi ies [50]. Recen ly, in o de o look o low-powe -consump ion de ices,
displacemen a 500 m/s unde 6 MA/cm
2
ha e been p o en by he e ical injec ion o
spin cu en s [51]. This e idences ha con inuous imp o emen s a e s ill p omo ing he
e inemen o de ices wi hin he ICT ield.
1.4 Fu he applica ions o magne ic nanowi es
The non- ola ile esis i e memo y and he ace ack memo y p e iously p esen ed
a e wo special examples ha show he use ulness o nanowi es in nanoelec onics and
spin onics. Despi e i s s aigh o wa d geome y, his s uc u e wi h high aspec and
In oduc ion
33
su ace- o- olume a ios has clea po en ial o a wide ange o applica ions in di e se
ields and, pa icula ly in Nanomagne ism [52][53], magne ic nanowi es exhibi exci ing
p ope ies o be implemen ed in magne ic de ices.
He ea e , he discussion will be ocused on 3D magne ic nanowi es since his
speci ic a chi ec u e cons i u es he cen al opic o his hesis. In his sec ion, a gene al
o e iew o hei applica ions as building block o unc ional de ices is gi en [32].
1.4.1 Spincalo i onics
The d i ing o he magne ic momen h ough spin-pola ized cu en s has been
ex ensi ely s udied in magne ic nanos uc u es such as wi es con aining domain walls
[54] o e ical mul i-laye ed nanowi es [55]. Going one s ep u he , he in e ac ion
be ween spin cu en s and hea cu en s can also be in es iga ed, a new esea ch a ea
coined “Spincalo i onics” eme ging in ecen yea s. The moelec ic and he momagne ic
phenomena a e del ed in o he coupling o elec on and hea cu en s [56], demons a ing
ha he pola iza ion o he spin can be go e ned no only by elec ic ields bu also by
empe a u e g adien s and ice e sa. Since he magne ic s a e o a sys em can be
modi ied he mally, e o s ha e been de o ed o looking o magne ic de ices wi hin he
spincalo i onic scope. The he mal manipula ion and he in e ac ion be ween hea and
spin cu en s can lead o di e en applica ions such as hea senso s, he mome e s, was e
hea ecycle s, powe gene a o s, coole s, e c.
1.4.2 High equency de ices
The p opaga ion o elec omagne ic wa es and spin wa es in con ined geome ies
such as magne ic nanowi es can gi e ise o no el mic owa e de ices wo king up o he
THz equency ange. The in e ac ion be ween an inciden elec omagne ic wa e and a
magne ic nanos uc u e leads o new p opaga ion mechanisms and di ac ion
phenomena. Speci ically, complex a chi ec u es such as mul i-laye ed nanowi es and

Chap e 1
34
nano ubes a e s ill unexploi ed in his ield. The e o e, a la ge a ie y o po en ial
applica ions could a ise in he ollowing yea s in ICT o biomedical goals [57].
1.4.3 Biomedical applica ions
Magne ic nanowi es ha e a g ea unc ionali y in applica ions ela ed o medicine,
e.g., d ug deli e y o magne ic hype he mia [58][59]. The mo phology o hese nano-
objec s makes hem he ideal subs i u es o magne ic nanopa icles. In pa icula , he
adjus men o hei magne ic aniso opy and coe ci e ields by modi ying he diame e ,
leng h and composi ion, oge he wi h he uning o he magne oc ys alline aniso opy,
plays a c ucial ole in he con ol o hei magne ic p ope ies and beha iou by he
applica ion o ela i ely low ex e nal magne ic ields —on he o de o 1 T— a a
dis ance.
Fi s ly, he in insic magne ic ea u es o hese nanos uc u es allow using hem as
hyb id magne o-op ical sys ems. Nanowi es composed by sec ions wi h di e en na u e
along he leng h can be ei he magne ically o op ically esponsi e o di e en s imuli,
being a g ea choice o be key componen s in sensing de ices [60].
Also, he cell apping and sepa a ion p ocedu es a e bene i ed om magne ic
nanowi es wi h high magne ic induc ion and aspec a io, educing he equi ed magne ic
ields o be used in compa ison wi h o he a chi ec u es [61]. The selec i i y in he
manipula ion o cells in cul u e media has been imp o ed as he nanowi e leng h is
co ela ed wi h he cell diame e . In his case, he aniso opic shape o he magne ic
nanowi es p o ides be e ou pu han he magne ically iso opic nanopa icles.
Rega ding disease ea men s, he bio unc ionaliza ion o magne ic nanowi es
allows a oiding he damages induced by he adi ional cance he apies. The g ea e
speci ici y o magne ic hype he mia enables he dea h o malignan cells by loca ing he
unc ionalized nanowi es on he umou and inducing hea by al e na ing magne ic ields
in he ange o kHz. In compa ison wi h nanopa icles, Fe nanowi es educe he ime
In oduc ion
35
equi ed in he ea men s due o hei shape and be e magne ic pe o mance beha iou
[62].
Magne ic nanowi es can also be used as magne ic nanoac ua o s on di e en
biological sys ems. In pa icula , Co nanowi es we e used o apply e y accu a ely
con olled o ces o li ing cells h ough magne ic ield-induced o que [63], obse ing
mechanical s ess esponses which can be e y e icien in cell ea men s.
1.4.4 Magne ic Fo ce Mic oscopy ips
The high aspec a io, coe ci i y and small la e al esolu ion o magne ic nanowi es
make hem pe ec candida es o wo king as Magne ic Fo ce Mic oscopy (MFM) ips.
Among he se e al me hods used o he ab ica ion o hese nanowi es on op o he
s anda d A omic Fo ce Mic oscopy (AFM) p obes [64][65], Focused Elec on Beam
Induced Deposi ion eme ges as one o he mos p omising echniques due o he p ecise
con ol o he deposi ion posi ion and il angle wi h espec o he a ge sample [66].
Fu he de ails o his opic will be hea ily discussed in Chap e 6.
Figu e 1.5. Diag am o a 3D Fe nanowi e g own by FEBID on o an AFM p obe. The inse
shows an SEM image o he s uc u e used o MFM measu emen s [66].
1.4.5 Magne oplasmonics
Plasmons a e collec i e exci a ions o he conduc ion elec ons o a me al induced
by incoming elec omagne ic adia ion. The magne ic beha iou o ce ain ma e ials
allows con olling he plasmonic p ope ies o he s uc u es by he applica ion o ex e nal
magne ic ields. This leads o he de elopmen o ac i e magne oplasmonic de ices wi h
applica ions om elecommunica ions o biosensing [67].
Chap e 1
36
Howe e , he magne oplasmonic s udies a e gene ally limi ed o nanopa icles and
ilms, wi h sca ce in es iga ions on e omagne ic nanowi es [68]. Speci ically, hei
combina ion wi h plasmonic ma e ials such as Au o P could gi e ise o mul i unc ional
objec s o his unexplo ed ield. This esea ch line has a long oad ahead wi h p omising
applica ions in op ical biochemical sensing de ices o nanopho onics [69].
1.5 Design and ab ica ion o magne ic nanowi es
In o de o ensu e p ope ope a ion o he applica ions p esen ed p e iously,
ad anced ab ica ion echniques a e equi ed. In his sec ion, di e se app oaches o he
c ucial nano ab ica ion mains ay o magne ic nanos uc u es will be ackled. Di e en
bo om-up and op-down app oxima ions de o ed o building magne ic nanowi es,
pa icula ly in 3D, will be e iewed o a be e unde s anding o hei ad an ages [70].
1.5.1 Elec ochemical syn hesis
The elec ochemical deposi ion, commonly used in esea ch and indus y, is a
bo om-up echnology which consis s o an elec oly ic p ocess whe e, applying a cu en
o ol age, he me allic ions o an elec oly e a e educed, c ea ing a solid deposi on he
ca hode elec ode. Rega ding nanowi es g ow h, he concep en ails he deposi ion o he
ma e ial inside he po es o channels o a memb ane, leading o s uc u es wi h he desi ed
a chi ec u e. Al hough he empla e me hod can be employed in combina ion wi h o he
echniques, he elec ochemical deposi ion cons i u es a commonly used app oach o ill
he po ous memb anes wi h magne ic ma e ials. Depending on he ype o bias applied o
he elec oly e, as men ion below, di e en elec odeposi ion echniques can be explo ed.
On he one hand, i is wo h men ioning he po en ios a ic elec odeposi ion, based
on a p ese a ion o he po en ial in he wo king elec ode wi h espec o he e e ence
one. This ype o deposi ion e e s o one o he mos common echniques o g owing
Fe, Co and Ni nanowi es and alloys be ween hem [71][72]. On he o he hand, he
gal anos a ic elec odeposi ion elies on he applica ion o a cons an cu en densi y and
In oduc ion
37
has been used o he ab ica ion o magne ic alloy nanowi es and mul i-laye ed
a chi ec u es [73][74]. In compa ison wi h he po en ios a ic p ocess, i is a mo e p ecise
me hod in e ms o he g ow h a e, implying a be e con ol o he olume o deposi ed
ma e ial by go e ning he deposi ion ime.
Addi ionally, pulse elec odeposi ion, oo ed in he combina ion o po en ios a ic
and gal anos a ic pulses ollowed by an in e media e eco e ing s ep, could gi e ise o
co e-shell Fe@FeO
x
o Ni@NiO nanowi es ob ained a e an oxida ion p ocess once he
nanos uc u es a e ou o he empla e [75]. Besides, as shown in Figu e 1.6,
mul isegmen ed FeCo/Cu nanowi es ha e been ab ica ed elec ochemically by pulse
elec odeposi ion al e na ing he ol age be ween -1.8 and -0.7 V o he FeCo and Cu
segmen s, espec i ely. Mo eo e , modi ying he pulse imes, he leng h o each segmen
can be uned [58].
The limi a ion o use conduc i e subs a es o mos o he elec odeposi ion
me hods can be o e come by using he al e na ing cu en elec odeposi ion. This
s a egy allows gua an eeing ha he ypical passi a ion oxide laye on op o he
subs a es will no be cha ged o pola ized. In his way, me allic and semiconduc o
s uc u es ha e been commonly ab ica ed wi h a di ec con ac o he subs a e [76].
Among he huge numbe o a iables which should be con empla ed o a success ul
g ow h, e.g., ba h pH, empe a u e o elec oly e composi ion, i should also be poin ed
ou a co ec le el o we abili y in he po e wall o a ou he in il a ion o he p ecu so
inside he channel, o he con ol o he sh inkage a ay du ing he solidi ica ion o he
ma e ial. This means ha he widely used empla e-assis ed me hod mus be employed
unde op imized condi ions, ypically using o de ed nanopo ous anodic Al
2
O
3
empla es
[77][78]. To ob ain he desi ed nanos uc u e geome y, he dimensions o he empla e
(po e diame e and leng h, and he dis ance be ween he po es) mus be uned. All hese
pa ame e s will de e mine no only he mo phology and s uc u al ea u es, bu also he
magne ic p ope ies o he nanowi es.
Chap e 1
44
1.5.5 Quenching and d awing echnique
The ab ica ion o amo phous glass-coa ed mic o- and nanowi es has been ca ied
ou ollowing he common quenching and d awing me hod, also called glass-coa ed mel
spinning [107]. This apid solidi ica ion echnique is used o he ab ica ion o s uc u es
wi h diame e s anging om ens o nanome es o millime es, ailo ing he la e al
dimension by adjus ing he empe a u e o he p ecu so alloy and he cooling p ocess
[108]. A e op imiza ion, he g ow h o Co
68.15
Fe
4.35
Si
12.5
B
15
and Fe
77.5
Si
7.5
B
15
nanowi es
wi h me allic co e diame e s be ween 90 and 180 nm we e p epa ed o he i s ime in
2011 [109].
This echnique p esen s some ad an ages wi h espec o o he li hog aphy and
elec odeposi ion s a egies. I is no only a cheap and s aigh o wa d me hod, wi h no
limi a ion in e ms o he nanowi e leng h, bu also allows uning he composi ion,
magne iza ion, magne ic aniso opy, swi ching magne ic ield, domain wall mo ion, e c.
All hese possibili ies should be conside ed o de elop u u e logic and sensing de ices.
1.5.6 Focused Elec on Beam Induced Deposi ion
S udies on undamen al p ope ies and echnological applica ions o magne ic
nanowi es equi e a ep oducible ab ica ion echnique which p o ides single and
isola ed objec s in a ge ed posi ions. These speci ica ions can be ul illed by Focused
Elec on Beam Induced Deposi ion (FEBID) echnique, which plays a c ucial ole in he
design and ab ica ion o many ypes o a chi ec u es allowing g ea e sa ili y in shape,
composi ion and magne ic ea u es [110][111][112]. Since he nanos uc u es p esen ed
in his hesis ha e been ab ica ed by his echnology, b ie ema ks will be done in his
subsec ion and comp ehensi e explana ions will be add ess h oughou he manusc ip .
The me hod, in oduced o he i s ime by S. Ma sui in 1984 [113], consis s o a
p ecu so gas decomposi ion by an elec on beam, e en ually p oducing a solid ma e ial
only in he a eas whe e he elec on beam scans. This single-s ep nanoli hog aphy p ocess

In oduc ion
45
does no equi e he use o masks, esis s o li -o p ocedu es. I is, howe e , in luenced
by a g ea numbe o pa ame e s such as he elec on beam ol age and cu en , p ecu so
gas lux, e c. which need o be con olled and op imized.
Composi ional, elec ical and magne ic p ope ies ha e been widely in es iga ed in
2D Co and Fe nanowi es [114][115][116][117], pu ing o wa d applica ions such as he
ones based on di ec nanomagne logic de ices o compu e bina y in o ma ion o
nanosenso s [116][118]. The nex na u al s ep was o mo e in o 3D deposi s, whe e la ge
e sa ili y in e ms o shape can be ob ained. In addi ion, he speci ic ab ica ion o 3D
nanowi es esul s in highe a eal densi y and no el domain wall con igu a ions. This has
led o he FEBID design o magne omechanical nanoac ua o s [119] o MFM ips [120],
and could gi e ise o he cons uc ion o he 3D ace ack memo y. Howe e , sca ce
in es iga ions ha e been pe o med along his line and challenges s ill emain o his
ou -o -plane (OOP) a chi ec u es [121]. Wi h his mo i a ion in mind, his hesis is
de o ed o he in-dep h s udy o he g ow h and cha ac e iza ion o 3D e omagne ic
nanowi es g own by FEBID.
Figu e 1.12. Schema ic diag am o some (a) 2D and (b) 3D geome ies examples and hei
magne ic con igu a ions [70].
Chap e 1
46
1.6 Ou line o he hesis
This hesis is ocused on in es iga ing he mul i ude o aspec s ela ed o he
de elopmen o 3D magne ic nanowi es by FEBID and hei cha ac e iza ion h ough
ad anced echniques. I includes he explo a ion o he ab ica ion condi ions and g ow h
modes (Chap e 3), he pos -g ow h op imiza ion o hei physical p ope ies (Chap e 4),
he o ma ion o new a chi ec u es and he e os uc u es (Chap e 5), and applica ions
(Chap e 6).
Hi he o, in Chap e 1 he b ie his o ical o e iew abou he cu en and u u e
applica ions o magne ic nanowi es and he di e en me hods used o ab ica e hese
p omising nano-objec s ha e been desc ibed. This gene al pe spec i e has been aimed o
se e as a s a ing poin o a ouse cu iosi y in o he eade , p esen a gene al amewo k
o his manusc ip and in oduce some o he concep s which will be discuss he ea e .
In Chap e 2, desc ip ions o he undamen al expe imen al echniques employed o
he g ow h and cha ac e iza ion o 3D nanowi es a e gi en. Special emphasis will be
placed on FEBID nano ab ica ion echnology, and in composi ional and magne ic
cha ac e iza ion by T ansmission Elec on Mic oscopy (TEM) echniques.
Chap e 3 is de o ed o explaining how uning he shape, composi ion and
magne iza ion o hese e ical nano-objec s is possible due o he g ea e sa ili y o
FEBID and i s combina ion wi h o he s a egies. Pa icula men ion should be gi en o
he new ARchi ec u al Adjus men by G id O e lay Nano echnology (ARAGON) Chip,
allowing he ab ica ion o FEBID nanos uc u es on insula ing subs a es —which had
been impossible un il now—, and p esen ing an addi ional deg ee o eedom o modula e
dimensional pa ame e s o he nanos uc u es.
Chap e 4 discusses di e en app oaches o he imp o emen and op imiza ion o
s uc u al, composi ional and e omagne ic p ope ies o he nanowi es. Speci ically, in
si u and ex si u pos -g ow h annealing ea men s ha e been explo ed o enhance he
c ys allini y, me allic con en and magne ic induc ion o he nanos uc u es.
In oduc ion
47
In Chap e 5, he implemen a ion o he co e-shell a chi ec u e o he g ow h 3D
FEBID Co@P and Fe@P nanowi es is de eloped. This aims a minimizing he
deg ada ion o he e omagne ic p ope ies o he co e caused by i s na u al su ace
oxida ion o a non- e omagne ic ma e ial. Addi ionally, his s a egy was used o
ab ica e e omagne ic P @Co nano ubes and in es iga ing hei magne ic beha iou .
Chap e 6 explo es some possible applica ions o 3D e omagne ic nanos uc u es
g own by FEBID. Special a en ion will be paid o op imiza ion o s aigh e ical
nanowi es o MFM measu emen s in di e en en i onmen s, and o he design o mo e
complex 3D a chi ec u es based on hook-shaped nanowi es aimed o domain wall
condui de ices.
Finally, Chap e 7 gi es a comp ehensi e o e iew o he key esul s o he hesis,
summa ize he main conclusions and discusses some u u e pe spec i es o 3D FEBID
g ow h in he ield o Nanomagne ism.
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V. M. P ida and B. He nando, “Templa e-assis ed CoPd nanowi e a ays:
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magne ic p ope ies and FORC analysis”, J. Nanosci. Nano echnol. 12, 4736
(2012).
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Bakonyi, “Gian Magne o esis ance in Co-Cu/Cu Mul ilaye s P epa ed by
Va ious Elec odeposi ion Con ol Modes”, J. Elec ochem. Soc. 150, C507
(2003).
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K. Kim, “Syn hesis and Cha ac e iza ion o Fe - FeO
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Co e-Shell Nanowi es”,
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Chap e 2
60
Figu e 2.1. Schema ic diag am o a Dual Beam SEM-FIB sys em.
The piezoelec ic pla o m can be mo ed in he h ee spa ial di ec ions, o a ed 360
deg ees and il ed a any angle be ween -10 and 60 deg ees. The acuum sys em is
comp ised by ou ion ge e pumps wo king on he columns, and o a o y and
u bomolecula pumps ac ing on he wo king chambe , eaching p essu es below ~10
-7
mba in he columns (~10
-10
mba in he gun compa men s) and a ound 1 × 10
-6
mba in
he wo king chambe .
The image acquisi ion elies on he undamen al basis o a scanning mic oscope.
The p ima y beam is scanned by he scan coils o e a su ace a ea o he sample ollowing
a desi ed pa e n called as e , usually a squa e pa e n de ined by he scan uni . No mally,
his scan en ails a se ies o lines in he ho izon al di ec ion o a plane, sligh ly shi ed by
he scan coils om one ano he in he e ical di ec ion using he scan gene a o . The
in e ac ion be ween he p ima y beam and he sample gene a es pa icles and adia ion

Expe imen al echniques
61
which can be collec ed by he di e en de ec o s while he beam scans. A e da a
p ocessing, he inal image is displayed in he compu e sc een. I is use ul o place he
specimen in he eucen ic heigh , enabling simul aneous imaging using elec ons and ions
when il ing he s age.
The SEM column is gene ally de o ed o imaging. The elec on-sample in e ac ion
b oadly gene a es seconda y elec ons (SE), backsca e ed elec ons (BSE), cha ac e is ic
X- ays, Auge elec on and ca hodoluminescence ( isible ligh ). In ou case, SE and BSE
a e he mos used pa icles o imaging ope a ion. The SE a e gene a ed by he inelas ic
sca e ing o he p ima y beam wi h he alence elec ons o he ou e shells o he sample
a oms. They a e emi ed wi h ene gies lowe han ~50 eV, ha ing mean ee pa hs below
50 nm. Thus, since only he su ace ones can escape and be de ec ed, hey a e used o
ob ain images o opog aphic con as . On he o he hand, he BSE a e gene a ed by he
quasi-elas ic sca e ing o he p ima y beam wi h he nuclei o he a oms. Thus, he ene gy
los by hese elec ons is e y li le, being he momen um ans e la ge, allowing he
elec ons o be sca e ed a high angles and equen ly backsca e ed. As BSE a e high-
ene gy elec ons, hey also come om he deepe egions o he sample and do no gi e
accu a e mo phological in o ma ion. Howe e , hey p o ide images wi h composi ional
con as : he sca e ing c oss sec ion o he BSE inc eases wi h he a omic numbe , ;
he e o e, he a eas con aining hea y elemen s a e b igh e han ha o he ligh e ones
in he SEM images.
Figu e 2.2. Basic diag am o he e en s caused by he beam-sample in e ac ion.
Chap e 2
62
In he case o FIB, he use is no limi ed o imaging. The ion-sample in e ac ion
gene a es SE, seconda y ions and ion implan a ion, among o he s. When he kine ic
ene gy o he ion beam exceeds he binding ene gy o he a ge ma e ial, he physical
spu e ing o he a oms occu s, hus he milling o he ma e ial su ace. These e en s can
also induce amo phiza ion and ola iliza ion o he i adia ed egion o he specimen [24].
The de ec o s ins alled in he sys em a e usually he E e ha Tho nley de ec o
(ETD), he Th ough Lens de ec o (TLD) and he Ion-Con e sion and Elec on de ec o
(ICE). The ETD is a scin illa o pho o-mul iplie de ec o which collec s SE, BSE and
seconda y ions. The TLD is mainly used o high esolu ion imaging and collec s bo h
SE and BSE. The ICE is a cha ged pa icle de ec o which collec s seconda y ions, SE
and BSE. In ou case, mainly ETD and TLD, and in lesse ex en ICE, ha e been used o
acqui e images collec ing SE. In addi ion, h ee wo king modes can be selec ed o une
he inal pe o mance: he ield- ee mode, he imme sion mode and he Ene gy-
Dispe si e X- ay Spec oscopy (EDS) mode. The ield- ee mode gene ally assis s
na iga ion a low magni ica ions and can be used wi h ETD and ICE de ec o s. Mo eo e ,
an in a ed cha ge-coupled de ice (CCD) came a allows he inne pa o he wo king
chambe o be obse ed and is used o spa ial o ien a ion o he sample. The imme sion
mode is used o ul a-high- esolu ion imaging, swi ching on he imme sion lens
(applying a magne ic ield o collec mo e elec ons) and no mally collec ing he SE wi h
he TLD de ec o . Finally, he EDS mode is sui able o X- ay spec oscopy, educing he
powe o he imme sion lens and imp o ing he X- ay signal. Fo his pu pose, an EDS
de ec o is moun ed o collec X- ay pho ons coming om he sample.
Fu he mo e, he equipmen is i ed wi h a gas injec o sys em (GIS) o med by a
se o injec o s con aining p ecu so ma e ial, which can be deli e ed locally on he
su ace subs a e hanks o a s ainless-s eel needle and a e y na ow nozzle. A hea e
egula es he empe a u e inside he GIS o he en h o a deg ee, so an op imum alue
can be achie ed, high enough o sublima e he p ecu so while p e en ing i s he mal
Expe imen al echniques
63
decomposi ion inside he c ucible. I a cons an empe a u e is eached, a speci ic s eady
p essu e is ob ained. This implies ha , i he acuum in he wo king chambe is kep
cons an , he gas lux jus depends on he sa u a ed apo p essu e o he p ecu so and
on he esis ance due o he needle wall. The p ecu so s used in his hesis and hei
ope a ion empe a u es a e: dicobal oc aca bonyl, Co
2
(CO)
8
, a ~27 ºC; dii on
nonaca bonyl, Fe
2
(CO)
9
, a ~28 ºC; ime hyl me hylcyclopen adienyl pla inum,
CH
3
C
p
P (CH
3
)
3
a ~45 ºC; and ungs en hexaca bonyl, W(CO)
6
, a ~55 ºC.
The sys em is also equipped wi h a nanomanipula o (Omnip obe
®
), used o p ecise
sample mechanical ope a ions in speci ic p ocedu es such as lamella p epa a ion. Finally,
an an i- ib a ion sys em o minimize mechanical ins abili ies is placed in he g ound.
Figu e 2.3. Image o he main componen s o a Dual Beam sys em: (A) SEM column, (B)
FIB column, (C) p ocess chambe , (D) gas injec o sys em, (E) nanomanipula o , (F) TLD
de ec o , (G) ETD de ec o , (H) ICE de ec o , (I) CCD came a and (J) so wa e o he sys em.
Chap e 2
64
Th ee comme cial Dual Beam sys ems ha e been used: wo FEI Helios NanoLab
600 and 650, ins alled in he Class 10000 clean oom o he Labo a o io de Mic oscopías
A anzadas (LMA) loca ed in he Ins i u o de Nanociencia de A agón (INA) a he
Uni e sidad de Za agoza, and he FEI No a 200 NanoLab o he Ins i u ü
Elek onenmik oskopie und Nanoanaly ik - Zen um ü Elek onenmik oskopie
(FELMI-ZFE). E en hough hese ins umen s p esen some mino di e ences, he wo k
is pe o med simila ly in all o hem.
2.1.1.1 Focused Elec on Beam Induced Deposi ion
FEBID is a single-s ep nanoli hog aphy echnique based on he deli e y o
p ecu so gas molecules close o he subs a e, subsequen ly adso bed on he su ace, and
e en ually dissocia ed by a inely- ocused elec on beam p oducing a deposi o solid
ma e ial [25][26][27][28].
Be o e he consolida ion o FEBID, he po en ial o elec on beam induced
p ocessing o pa e ning was hin ed in he 1970s by he local deposi ion o con aminan s
in SEM [29]. When he SEM scans a egion, a laye o a ew nanome es s a s o co e
he scanned a ea. This phenomenon is p oduced by he decomposi ion o hyd oca bons
p esen in he acuum chambe as esidual gases and adso bed on he scanned su ace.
The echnique was o mally in oduced in 1984 by S. Ma sui [30][31], injec ing di e en
p ecu so gas molecules on pu pose inside he acuum chambe p oducing nanos uc u es
wi h dis inc unc ionali ies. The las 30 yea s ha e wi nessed he inc easing in e es o
he scien i ic communi y and indus y in he de elopmen o FEBID. Nowadays, his
me hod is capable o nanome e-scale esolu ion o he g ow h o 2D [32] and 3D [33]
s uc u es. This unique capabili y o FEBID has been exploi ed in a b oad ange o
applica ions, such as in eg a ed ci cui edi and mask epai [34], c ea ion o elec ical
con ac s [35], g ow h o magne ic nanowi es [36], ab ica ion o plasmonic
nanos uc u es [37], pho ode ec ion [38], gas sensing [39], e c.; hus becoming a key
li hog aphic echnique in Nano echnology [40] and Ma e ials Science [41].
Expe imen al echniques
65
Once he p ecu so gas molecules a e injec ed locally nea he subs a e su ace,
some o hem a e dissocia ed by he elec on beam. The non- ola ile pa o he gas is
deposi ed whe eas he ola ile one is pumped ou o he wo king chambe . The shape o
he deposi is de ined by he elec on beam scan as well as he complex in e ac ions
be ween elec on beam, subs a e, p ecu so molecules and he g owing s uc u e
[42][43]. Fo ins ance, he di usion, adso p ion and deso p ion phenomena o he
molecules o e he subs a e o he p obabili y o an elec on o b eak he molecule bonds,
mainly ela ed o he elec on ene gy, a e c ucial ing edien s o unde s and he g ow h
p ocesses and de e mine how he ab ica ion p ocess akes place.
The FEBID is also go e ned by many di e en pa ame e s which mus be con olled
o ob ain he desi ed nanos uc u es: he elec on beam ol age, elec on beam cu en ,
dwell ime, e esh ime, o e lap, pi ch, scan di ec ion, pa e n dimensions, p ecu so gas
lux, e c. These a iables will be discussed in Chap e 3, gi ing some de ails abou hei
main unc ions and capabili ies.
Figu e 2.4. Diag am o he FEBID p ocess using Co
2
(CO)
8
as gas p ecu so .

Chap e 2
66
2.1.2 Op ical li hog aphy
The op ical li hog aphy is based on he ab ica ion o mic os uc u es by ans e ing
a pa e n in o a wa e using masks and pho osensi i e ma e ials which a e subsequen ly
de eloped wi h ul a iole (UV) ligh . The p ocess consis s o se e al s eps in sequence
o ob ain he inal sys em.
In he basic p ocess, a pho osensi i e chemical pho o esis is sp ead all o e he
sample, al eady g own on op o he subs a e, by spin coa ing. The pho o esis is a
iscous luid usually composed by a polyme , a pho osensi i e componen and a sol en .
The polyme supplies he iscosi y, adhe ence and esilience equi ed o he ul e io
chemical e ching; he pho osensi i e componen makes he pho o esis sensi i e o he
UV adia ion; and he sol en allows he polyme o be in solu ion and can be
subsequen ly elimina ed by so -baking. Two di e en ypes o pho o esis s can be used,
depending on i s solubili y upon UV i adia ion: posi i e and nega i e pho o esis s. In a
posi i e pho o esis , he UV ligh b eaks he polyme chains due o chemical eac ions
and he pho osensi i e complex inc eases i s solubili y, whe eas he non-i adia ed a eas
emain insoluble in he de elope . The p ocess is qui e he con a y o a nega i e
pho o esis : i is soluble in he de elope , while UV i adia ion induces c osslinking o
he polyme chains ha educes i s solubili y.
The desi ed pa e n is ans e ed in o he pho o esis using a pho omask, ypically
made o qua z wi h he mo i s imp in ed in ch omium. Qua z is anspa en o he UV
ligh and he ch omium abso bs his ype o ligh . A e he UV exposu e, he esis
becomes sensi ized, he sample is imme sed in he de eloping luid and he soluble a eas
a e emo ed. Then, d y o we e ching is pe o med o elimina e he ilm a eas
unp o ec ed by he esis , and so he pa e n is ans e ed o he sample. Finally, he
emaining non-sensi ized esis p ese ed on op o he emaining sample is emo ed by
using ace one.
Expe imen al echniques
67
In he li -o p ocedu e, he g ow h o he ilm is ca ied ou only a e he mo i s
ha e been ans e ed on o a laye o esis on he subs a e. Then, he sample is ab ica ed
co e ing he subs a e unp o ec ed egions and esis a eas, ensu ing ha he hickness o
he esis is a leas 50% highe han ha o he sample. This gua an ees ha he
unde nea h esis will be emo ed oge he wi h he sample deposi ed on op, keeping he
a eas whe e he sample is in di ec con ac wi h he subs a e. I a posi i e mask is used,
he sample pa e n is supplemen a y o ha o he mask and ob ained wi hou he e ching
s ep, in con as o he basic op ical li hog aphy p ocess.
The sys em used o op ical li hog aphy is he high-p ecision mask aligne SUSS
Mic oTec MA6 equipped wi h a Hg lamp exposu e sou ce, achie ing a esolu ion down
o ∼2 µm. I is ins alled in he Class 100 clean oom o he LMA-INA a he Uni e sidad
o Za agoza. Besides, a spin coa e and a ho pla e SUSS Mic oTec Del a 20T/200 a e
a ailable in he same oom o p oduce homogenous pho o esis coa ings unde a speed
up o 10
4
pm and hea i up o 250 ºC.
Fu he mo e, hin ilm g own in he li -o p ocess is pe o med in an elec on beam
e apo a o (E-beam PVD) Edwa ds 500 ins alled a he Class 10000 clean oom.
Thicknesses om 1 nm o 500 nm o me allic ma e ials can be deposi ed wi h a esolu ion
o 0.1 nm using a qua z balance o calib a ion. The base p essu e is ~2 × 10
-7
mba ,
ha ing ou di e en a ge s o deposi ma e ial.
When d y e ching is equi ed, he emo al o sample ma e ial is pe o med by
physical p ocesses using Ion Beam E ching (IBE). In his case, a beam o ine ions
spu e s he sample su ace elimina ing ma e ial in a uni o m and homogeneous way. This
has been ca ied ou in he IBE SISTEC 600 equipmen , i ed wi h a gon gas, wo king
a 2 × 10
-7
mba and equipped wi h a adio equency gene a o a 13.56 Hz and 600 W.
Chap e 2
68
Figu e 2.5. Images o (a) he mask aligne SUSS Mic oTec MA6, and (b) he
spin coa e and
(c) ho pla e SUSS Mic oTec Del a 20T/200
equipmen o op ical li hog aphy.
Figu e 2.6. Images o (a) he
Ion Beam E ching and Milling SISTEC 600 and
(b) he
elec on-beam e apo a o (E-beam PVD) Edwa ds 500.
2.2 T ansmission Elec on Mic oscopy
TEM is a nanocha ac e iza ion echnique based on he o ma ion o an image wi h
he elec ons ansmi ed h ough a hin specimen i adia ed wi h a high-ene gy elec on
beam, o ypically 80-300 keV.
The spa ial esolu ion o an op ical sys em is limi ed by he adia ion wa eleng h, .
E en hough esidual abe a ions in oduced by he elec on op ics o he mic oscope, as
Expe imen al echniques
69
well as mechanical, elec onic and he mal ins abili ies, deg ades he esolu ion powe ,
mode n mic oscopes ou inely p o ide a omic esolu ion, ∼2 Å, and las -gene a ion
abe a ion co ec ed mic oscopes imp o e his alue down o he sub-Å ange [44].
When he p ima y elec on-specimen in e ac ion akes place, mul iple e en s a e
o igina ed, such as SE, BSE, cha ac e is ic X- ays, Auge elec on, ca hodoluminescence
( isible ligh ), inelas ic sca e ing, elas ic sca e ing, he mal di use sca e ing and
B emss ahlung X- ays [45].
The mic oscope is di ided in h ee main pa s: he elec on gun; he column, which
includes he illumina ion sys em, he objec i e lens and he imaging sys em; and, he
came a sec ion. The elec on sou ce, loca ed in he uppe pa o he machine, is
composed by an emi e wi h an elec os a ic lens (e.g., Wehnel elec ode in a he mionic
gun o gun lens in a FEG). Then, he illumina ion sys em, placed in he column, s a s o
de ine he way he elec ons will i adia e he specimen. I is composed by a se o
condense lenses (usually wo o h ee) and condense ape u es de o ed o de ining he
beam cu en , size and con e gen angle.
The mic oscope can be con igu a ed o p o ide a b oad beam illumina ion o he
specimen, o en known as TEM mode, o a con e gen beam o o m a small (sub-nm)
p obe. The la e is used in Scanning T ansmission Elec on Mic oscopy (STEM) mode,
whe e his con e gen p obe is scanned o e he specimen in a simila ashion as in SEM.
To op imize and p o ide e sa ili y o hese ypes o illumina ion, a condense mini lens
loca ed be o e he objec i e lens is s ong exci ed (TEM mode) o weak exci ed (STEM
mode).
Nex o he egion whe e he EDS de ec o a e placed, he objec i e lens is de o ed
o o ming he i s image o he sample, hus being de e minan o he ul ima e
esolu ion. I is disposed a e he illumina ion sys em and is ypically composed by wo
lenses called objec i e condense lens and objec i e imaging lens, con o ming he uppe
and lowe polepieces, espec i ely. These win lenses a e symme ically placed, and hei
Chap e 2
76
elec ons o a speci ic ene gy loss. As a esul , a spec um is o med by ep esen ing he
in ensi y and he ene gy loss. Many pa ame e s can be con olled such as he spec ome e
ene gy esolu ion, en ance ape u e, collec ion angle, objec i e ape u e diame e ,
came a leng h, e c. Fu he de ails and speci ic alues will be gi en du ing he nex
chap e s as he expe imen s a e p esen ed.
Th ee di e en spec ome e s ha e been used: a T idiem 863 Ga an Ene gy Fil e
(GIF) ins alled in he FEI Tecnai F30 TEM; a T idiem 866 ERS GIF in he FEI Ti an
Low Base 60-300; and a GIF Quan um in he FEI Ti an Cube G2 60-300 [52].
2.2.1.2 Ene gy-Dispe si e X- ay Spec oscopy
The EDS sys em is based on he analysis o X- ay pho ons coming om he sample.
This p ocess comes abou when he elec on beam exci es an elec on o he inne shell
o he a om, gene a ing a hole. Subsequen ly, elec ons om a highe -ene gy shell
occupies he c ea ed hole, p oducing X- ays in cascade wi h disc e e, cha ac e is ic
ene gies co esponding o he di e ence be ween ene gy le els o he a om [53].
Since he X- ays ha e speci ic ene gies which depends on he ene gy di e ence
be ween wo a omic le els and each chemical elemen has a unique a omic s uc u e, EDS
echnique p o ides in o ma ion abou he chemical composi ion o he sample. In he
EDS spec a, whe e he numbe o coun s as a unc ion o he ene gy is ep esen ed, each
peak is associa ed wi h one elec onic ansi ion o a single elemen [54].
The EDS sys em is composed by he de ec o , he p ocessing elec onics and he
compu e . Fi s ly, he de ec o gene a es a cha ge pulse which is p opo ional o he
pho on ene gy, con e ing i o a ol age signal be o e ampli ying i by means o a ield-
e ec ansis o . Then, he pulse is iden i ied elec onically, and a digi al signal is s ocked
in he co esponding channel alloca ed o ha speci ic ene gy displaying he spec um.
In his hesis, h ee di e en EDS sys ems ha e been used a he INA: he APOLLO
X de ec o associa ed wi h he EDAX so wa e and moun ed in he FEI Helios NanoLab

Expe imen al echniques
77
650; he EDAX 136-5 de ec o coupled wi h he Genesis RTEM so wa e embedded in
FEI’s TIA so wa e ins alled in he FEI Tecnai F30 TEM; and, he Ox o d INCA 200
EDS se up om Ox o d Ins umen s se in he FEI Helios NanoLab 600.
2.2.1.3 O -Axis Elec on Holog aphy
O -Axis EH is an in e e ome ic echnique which measu es he ampli ude and he
phase shi o he elec on wa e ansmi ed h ough he specimen. This phase shi is
di ec ly ela ed o he elec omagne ic ields p oduced by he sample, which can be
de e mined in a quan i a i e way.
The beha iou o a ela i is ic elec on wa e, , in an elec omagne ic ield is
desc ibed by he Di ac equa ion:
1
2


=

−

ℏ
∇
+










=



∗
+







(2.1)
whe e 

is he es mass o he elec on, ℏ he educed Planck cons an ,  he elec on
cha ge,  he magne ic po en ial,  he elec ic po en ial, =1+
∗




⁄ he
ela i is ic Lo en z ac o and 
∗
he ela i is ic accele a ing po en ial. The solu ion o
he equa ion is he objec wa e unc ion whose phase shi , !,#, is al e ed by he
Aha ono -Bohn e ec [55]. Pa icula ly, he phase shi o an elec on wa e ad ancing
along he $ axis and passing h ough a magne ic specimen wi h neu al cha ge can be
exp essed ma hema ically as:

!
,
#

=
%


∗
&

'()

!
,
#
,
$

*$
−

ℏ
+
,
-

!
,
#
,
$

*!*$
(2.2)
whe e  is he elec on ela i is ic wa eleng h, 
'()
he mean inne po en ial and ,
-
he
magne ic induc ion ec o o hogonal o he uni a y ec o s along ! and $ axes [56].
A his poin , i should be in oduced he objec elec on wa e, 
./0
, de ined as he
ansmi ed elec on wa e unc ion in he exi su ace o he specimen. I a e y hin
Chap e 2
78
specimen is conside ed, he elec ons a e elas ically sca e ed and he abso p ion e ec s
can be neglec ed, gi ing ise o he ollowing equa ion:

.
/0




=
1




exp







(2.3)
whe e 1 is he ampli ude o he exi wa e unc ion and he phase shi induced by he
elec ic and magne ic po en ials o he specimen. Then, he objec i e lens o ms a
di ac ion pa e n and an image in he back ocal plane and he image plane, espec i ely.
In his p ocess, he objec i e lens in oduces abe a ions o he objec elec on wa e.
Thus, he objec elec on wa e in he back ocal plane, 
5677
, can be exp essed as a
unc ion o he equency 8
9

:

5677

8
9


=

./0

8
9


:

8
9


(2.4)
whe e :8
9

 is he phase con as ans e unc ion, a ma hema ical exp ession o he
modi ica ions o he elec on wa e caused by he ins umen (no by he specimen):
:

8
9


=


8
9


exp
;
−
<

8
9


=
exp
;
>

8
9


=
(2.5)
whe e 8
9

 is he ape u e- ela ed equency cu o , exp;−<8
9

= he damping
in oduced by mic oscope ins abili ies and >8
9

 he phase shi in oduced by he
abe a ions o he objec i e lens. In a i s app oxima ion, i low o de abe a ions (such
as s igma ism, coma) a e supp essed:
>

8
9


=
2
%

?
Δ
A
2


8

+
B
C
4

E
8
E
F
(2.6)
whe e Δ
A
is he de ocus and B
C
is he sphe ical abe a ion coe icien . As a esul , his
phase shi is ans e ed o he image, ul ima ely es ablishing he bases o he phase
con as imaging. None heless, since he image should be in ocus, and he magne ic
induc ion eme ged om he specimen induces small angula de lec ions (8≪), >8
9


Expe imen al echniques
79
can be neglec ed. In his case, he image elec on wa e, 
6HIJ
, and he in ensi y o he
image, K, a e:

6HIJ

8
9


=
L:
M
N
;

./0

8
9


:

8
9


=
≅
1




exp







=

6HIJ




(2.7)
K




=

6HIJ





6HIJ
∗




=
|
1




|

(2.8)
The image only con ains in o ma ion abou ampli ude a ia ions (which a e e y
small in hin specimens), and he phase in o ma ion, dependan o he elec ic and
magne ic ields, is los . To o e come his issue, EH enables he e ie al o he ampli ude
and he phase o he elec on wa e sepa a ely [57][58].
Expe imen ally, EH is based on he in e e ence be ween wo di e en elec on
wa es; a e e ence elec on wa e, 
Q7
, which p opaga es h ough he acuum, ideally
in e ac ing wi h no elec omagne ic ield; and he objec elec on wa e, 
./0
, ansmi ed
h ough he sample, which expe iences a phase shi by in e ac ing wi h any
elec omagne ic ield inside and a ound he specimen. The o e lapping and in e e ence
o 
Q7
and 
./0
is o igina ed by he de lec ion o he elec ons when a ol age is applied
o he elec os a ic Möllens ed bip ism, gene a ing he holog aphic inges. The BF
image o he specimen, o e lapped wi h he inge pa e n, is he so-called elec on
holog am [59][60].
F om he heo e ical poin o iew, in EH 
Q7
and 
./0
a e conside ed plane wa es:

Q7




=
exp
;

2
%
8
9

⋅


=
(2.9)

./0




=
1




exp
;

2
%
8
9

⋅


+





=
(2.10)
The wo wa es a e de lec ed by he bip ism S 2
⁄ and −S 2
⁄ angles along ! axis,
espec i ely.
Chap e 2
80
Figu e 2.8. Basic scheme o he EH echnique, ep oduced om [61] wi h pe mission.
This leads o he 
6TU
elec on wa e along ! axis in he supe imposing:

6TU




=
1




exp
V
−
%
S

!
+





W
+
exp
V
%
S

!
W
(2.11)
whose in ensi y K is:
K




=
|

6TU




|

=
1
+
1





+
2
1




cos
V
2
%
S

!
−




W
(2.12)
whe e 1+1

 con ains he in ensi y o he BF image, and he sinusoidal e m
ep esen s he in e e ence inges pa e n o he holog am wi h i s a gumen depending
only on he phase o he objec elec on wa e. The calcula ion o he Fou ie T ans o m
(FT) o he in ensi y leads o:
L:
|
K




|
=
[


+
L:

1





+
L:

1




exp








⨂
[
^
9

+
S

!
_
`
+
(2.13)
+
L:

1




exp

−







⨂
[
^
9

−
S

!
_
`
Expe imen al echniques
81
whe e ⨂ indica es he con olu ion ope a ion. In he ecip ocal space, he holog am is
o med by h ee di e en componen s: a cen al band and wo sidebands. The i s wo
e ms o he igh -hand side o he Equa ion 2.13 ep esen he cen al band and con ains
he BF image ela ed o he elas ic and inelas ic sca e ed elec ons wi h he ampli ude o
he objec elec on wa e. These do no s o e any de ail abou he phase, so hey ha e no
u he in e es o ob ain magne ic in o ma ion. On he o he hand, each sideband con ains
edundan in o ma ion abou he ampli ude and phase sepa a ely; hence, da a p ocessing
is only done wi h one o hem. The in e se Fou ie T ans o m (FT
-1
) o a cen ed sideband
allows he econs uc ion o he objec elec on wa e as he combina ion o an ampli ude
image and a phase image:
L:
M
N
;
L:

1




exp








⨂
[

9


=
=
1




exp







=

./0




(2.14)
whe e:




=
a c an
e
Im
;

./0




=
Re
;

./0




=
i
(2.15)
1




=
V
;
Im
;

./0




./0
=
=

+
;
Re
;

./0




./0
=
=

W
N

j
(2.16)
So a , his p ocess can be applied o any magne ic specimen. Howe e , in o de o
con inue wi h he p ocess de o ed o sepa a ing he elec os a ic and magne ic
con ibu ions, i is illus a i e o conside a speci ic example. Please, e e o Annex A
whe e he da a p ocessing is applied o e omagne ic nanowi es.
Two di e en TEM mic oscopes ha e been used o he EH expe imen s: he
comme cial FEI Ti an Cube 60-300 a he INA in Za agoza and he Hi achi I2TEM a he
CEMES-CNRS in Toulouse.

Chap e 2
82
2.3 Annealing echniques
The ab ica ion o nanos uc u es by FEBID echnique has some d awbacks which
can be o e come by annealing expe imen s. The me allic pu i y, he c ys allini y and he
magne iza ion o he deposi s is suscep ible o being imp o ed by his s a egy.
Two di e en annealing se ups ha e been used: a hea ing s age moun ed inside he
SEM Quan a FEG 250 ins alled a he INA in Za agoza and a hea ing chip Wild i e S3
om DENSsolu ions in he FEI Ti an Cube G2 60-300 a he FELMI-ZFE in G az.
The i s one, de o ed o ex si u expe imen s, is o med by a hea ing s age base which
holds all he componen s [62]. I includes wo disk-shaped insula ing elemen s made o
aluminous oam and a hea e placed be ween he insula o s consis ing o a mic o- u nace
in which samples a e hea ed om he sides, ensu ing empe a u e uni o mly dis ibu ed.
I is also equipped wi h a he mocouple, ce amic connec o s, a g aphi e c ucible o moun
he samples, wo ce amics pape s on op o educe hea losses and p o ec he insula o s
om damage, a co e pla e o ix he componen s and a hea shield o keep he
empe a u e homogeneous in he sample. In addi ion, i is i ed wi h a chambe eed-
h ough pla e, a wa e chille , a low box, wa e hoses and a mic op ocesso -con olle ,
de o ed o p o iding he desi ed empe a u e in he hea ing s age. The senso accu acy is
±1 ºC wi h an ope a ion ange om oom empe a u e o ∼1000 ºC wi h a maximum
hea ing amp o 50 ºC/min.
The second one is he TEM-hea ing sys em Wild i e S3 o in si u expe imen s. The
specimen is placed in a hea ing chip which includes mic o-elec o-mechanical sys ems
(MEMS) [63]. The subs a e includes o al holes whe e he suspended nanos uc u es can
be imaged. The chip is specially de eloped o ha ing small d i (<
1 nm/min a 800 ºC),
hea ing a es o 200 ºC/ms and image esolu ion o ~0.6 Å a 800 ºC. Then i is moun ed
in o he hea ing s age using a lock and ou pin connec ions o con ol he empe a u e.
Expe imen al echniques
83
Figu e 2.9. Images o (a) he hea ing s age moun ed in he SEM Quan a FEG 250, and (b) he
Wild i e S3 in si u TEM hea ing holde om DENSsolu ions.
2.4 Fu he magne ic cha ac e iza ion echniques
In his sec ion, h ee di e en expe imen al me hods employed o he magne ic
cha ac e iza ion o e omagne ic nanos uc u es a e desc ibed. The physical p inciples
o Supe conduc ing QUan um In e e ence De ice (SQUID) magne ome y, Magne o-
Op ical Ke E ec (MOKE) magne ome y and MFM will be ske ched.
2.4.1 Supe conduc ing Quan um In e e ence De ice magne ome y
The SQUID is used o measu ing changes in he magne ic ield ela ed o he
magne ic lux quan iza ion. I is conside ed one o he mos sensi i e magne ic lux
de ec o s, achie ing a ield esolu ion o 10
-17
T [64]. The p inciple which unde pins he
ope a ion o a SQUID is he quan iza ion o he magne ic lux [65][66]:
Φ
l
=
ℎ
2

≅
2
.
07
×
10
M
N
T
⋅


(2.17)
whe e Φ
l
is he magne ic lux quan um, ℎ is he Planck cons an and  he elec on
cha ge. The de ice is based on a supe conduc ing loop in e up ed by ei he one (RF-
SQUID) o wo pa allel Josephson junc ions (DC-SQUID) [67]. Explaining he basics in
he las case, he bias cu en en e s he loop and is di ided in o wo pa hs whe e he
Chap e 2
84
Josephson junc ions a e p esen by in oducing a e y hin insula ing laye . A magne ic
lux, Φ, h eads he supe conduc ing loop being an in ege numbe mul iple o he
elemen a y magne ic lux quan um, Φ
l
.
Two wa e unc ions ep esen he wo supe conduc ing a eas sepa a ed by he
Josephson junc ions wi h phases
N
and

:

N
=
|

|

6
u
(2.18)


=
|

|

6
u
w
(2.19)
Bo h wa e unc ions pene a e he hin insula ing laye and o e lap, hus Coope
pai s o elec ons unnel h ough he ba ie wi h a cu en , K
C
, which is p opo ional o
he phase di e ence be ween he wo supe conduc ing pa s a he insula ing laye [68]:
K
C
=
K
x
sin


−
N

(2.20)
whe e K
x
is he c i ical cu en . I a cons an bias cu en is kep , he ol age ac oss he
junc ions oscilla es wi h he phase change. A he same ime, he cu en lowing h ough
he SQUID is modula ed by he magne ic lux passing h ough he loop. Thus, measu ing
he ol age, he esponse o a change o lux can be de ec ed.
The SQUID equipmen used in his hesis was a home-made sys em de eloped by
D . Ma ía José Ma ínez-Pé ez om he Ins i u o de Ciencia de Ma e iales de A agón
(ICMA), Uni e sidad de Za agoza-Consejo Supe io de In es igaciones Cien í icas
(CSIC).
2.4.2 Magne o-Op ical Ke E ec magne ome y
Magne iza ion induces changes in he op ical p ope ies o he ma e ial. In pa icula ,
when pola ized ligh is e lec ed a magne ic su ace, i s pola iza ion and in ensi y a e
modi ied [69]. These changes o a pola ized lase beam a e e lec ing om a magne ized
Expe imen al echniques
85
sample su ace can be de ec ed by MOKE magne ome y, e en ually in e ing he
magne iza ion o he sample.
Fi s ly, he machine is ypically composed by a 3D mo ion s age o place he sample.
Also, a quad upole elec omagne su ounds he sample and can apply magne ic ields in
wo o hogonal di ec ions. The magne ic ields a e measu ed by senso s ins alled in o he
coils while an elec onic con ol loop adjus s he elec on cu en in he coils in eal ime
o p o ide he desi ed ield s eng h. In addi ion, he op ics head uni con ains he lase
op ics allowing he beam o lea e he head and come o a pola ize which selec s he ligh
pola iza ion. Then, he beam is ocused on he sample su ace by a se o lenses which
allows he lase o be inciden ei he no mal o he su ace o a 45 deg ees o he su ace
no mal [70]. A e he beam is e lec ed om he sample su ace, i is collima ed by a
lens and passes h ough an analyse . Then, he in ensi y and pola iza ion a e e alua ed.
The sys em shows he pola iza ion o a ion, also called Ke signal, as a unc ion o
he applied magne ic ield, ob aining he hys e esis loop. In gene al, his echnique
p o ides high sensi i i y and as measu emen imes, being conside ed an excellen
me hod o expe imen s on magne ic nanos uc u es [71], mic os uc u es [72] and hin
ilms [73].
Two di e en MOKE sys ems ha e been used: ew expe imen s we e pe o med in
he NanoMOKE
®
3 magne o-op ical magne ome e ins alled in he ICMA, Uni e sidad
de Za agoza-CSIC, and mos wo k has been pe o med in he MOKE equipmen se led
in he Ca endish Labo a o y a he Uni e si y o Camb idge.
2.4.3 Magne ic Fo ce Mic oscopy
The MFM echnique is a non-con ac mode o he scanning o ce mic oscopy based
on he de ec ion o magne ic ip-sample in e ac ions a he nanoscale. The me hod lies in
unde s anding and exploi ing he long- ange o ces a ising om he magne ic ields in
o de o in es iga e magne ic domain s uc u es [74].
Chap e 2
92
s udies o e omagne ic ocused elec on beam induced nanodeposi s”, Magne ic
Cha ac e iza ion Techniques o Nanoma e ials, Edi ed by C. S. S. R. Kuma ,
Sp inge (2017).
[62] FEI Company, “The Quan a FEG 250/450/650 Use Ope a ion Manual”, (2010).
[63] T. P. Almeida, D. McG ou he , Y. Pi ak, H. H. Pe ez Ga za, R. Temple, J.
Massey, C. H. Ma ows and S. McVi ie, “P epa a ion o high-quali y plana FeRh
hin ilms o in si u TEM in es iga ions”, J. Phys.: Con . Se . 903, 012022
(2017).
[64] R. L. Fagaly, “Supe conduc ing quan um in e e ence de ice ins umen s and
applica ions”, Re . Sci. Ins um. 77, 101101 (2006).
[65] B. S. Dea e and W. M. Fai bank, “Expe imen al e idence o quan ized lux in
supe conduc ing cylinde s”, Phys. Re . Le . 7, 43 (1961).
[66] R. Doll and M. Näbaue , “Expe imen al p oo o magne ic lux quan iza ion in a
supe conduc ing ing”, Phys. Re . Le . 7, 51 (1961).
[67] B. D. Josephson, “Possible new e ec s in supe conduc i e unneling”, Phys. Le .
1, 251 (1962).
[68] R. P. Feynman, R. B. Leigh on and M. L. Sands, “The Feynman lec u es on
physics”, Addison-Wesley Pub. Co. (1963).
[69] Z. Q. Qiu and S. D. Bade , “Su ace magne o-op ic Ke e ec (SMOKE)”, J.
Magn. Magn. Ma e . 200, 664 (1999).
[70] Du ham Magne o Op ics L d, “NanoMOKE
®
3 Use Manual”, (2012).
[71] S. Pa hak and M. Sha ma, “Magne o-op ical Ke e ec measu emen s on highly
o de ed nanomagne a ays”, J. Appl. Phys. 111, 07E331 (2012).
[72] Y. Jing an, R. Pé ez del Real, G. In an e and M. Vázquez, “Local magne iza ion
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magne o-op ical Ke e ec ”, J. Appl. Phys. 113, 043904 (2013).
[73] A. Be ge , S. Knappmann and H. P. Oepen, “Magne o-op ical Ke e ec s udy
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[74] U. Ha mann, “Magne ic o ce mic oscopy”, Ad . Ma e . 2, 550 (1990).
[75] L. M. Belo a, O. Hellwig, E. Dobisz and E. Dan Dahlbe g, “Rapid p epa a ion o
elec on beam induced deposi ion Co magne ic o ce mic oscopy ips wi h 10 nm
spa ial esolu ion”, Re . Sci. Ins um. 83, 093711 (2012).
[76] M. R. Koblischka, U. Ha mann and T. Sulzbach, “Imp o ing he la e al
esolu ion o he MFM echnique o he 10 nm ange”, J. Magn. Magn. Ma e .
272-276, 2138 (2004).
[77] G. Binnig, C. F. Qua e and C. Ge be , “A omic Fo ce Mic oscope”, Phys. Re .
Le . 56, 930 (1986).

Expe imen al echniques
93
[78] D. Ruga and P. Hansma, “A omic Fo ce Mic oscopy”, Physics Today 43, 23
(1990).
[79] O. Kazako a, R. Pu ock, C. Ba on, H. Co e-León, M. Jaa a , V. Neu and A.
Asenjo, “F on ie s o magne ic o ce mic oscopy”, J. Appl. Phys. 125, 060901
(2019).
Chap e 3: Tuning he g ow h o 3D
nanowi es by FEBID
This chap e co e s he capabili y o Focused Elec on Beam Induced Deposi ion o
ailo shape, composi ion and magne iza ion o 3D nanowi es. Pa icula ly, a
comp ehensi e s udy abou he complex mechanisms which go e n he g ow h p ocess
and s a egies unde aken o ailo hei physical p ope ies a e ackled. Fu he , a special
sec ion abou elec ically-biased me al s uc u e pa e ned on insula o s is add essed,
which allows ab ica ing nanos uc u es on insula ing subs a es and uning he la e al
dimension o 3D nano-objec s by elec ic biasing.
Chap e 3
96
3.1 P inciples o FEBID
FEBID elies on he decomposi ion o he p ecu so gas molecules deli e ed close
o he subs a e by a inely- ocused elec on beam, p oducing a deposi [1][2][3][4]. The
shape o he deposi is de e mined by he elec on beam scan as well as complex
in e ac ions be ween he elec on beam, subs a e, p ecu so gas molecules and he
g owing s uc u e [5][6]. Unde s anding he in luence o he FEBID pa ame e s is a key
poin o de elop p ope app oaches o he ab ica ion o nanos uc u es wi h op imum
p ope ies. Simul aneously, i is impo an o unde s and he mechanisms go e ning he
deposi ion o p o ide a comple e iew o his echnique.
The concu en con ol o he a ious pa ame e s ha play a ole in he g ow h
p ocess o nanos uc u es by FEBID is a daun ing ask [1]. The ene gy o he p ima y
elec ons, which is di ec ly ela ed o beam accele a ion ol age, and he elec on beam
cu en , de ined as he elec on low eaching he sample su ace, a e wo o he mos
impo an a iables. Howe e , one should also poin ou o he pa ame e s ela ed o he
elec on beam scan such as he dwell ime, which iden i ies he lapse o which he
elec on beam is held s ill on a pa icula poin ; he e esh ime, which is he pe iod o
ime be ween he s a o wo consecu i e loops and allows p ecu so gas eplenishmen
du ing he ime whe e he beam is paused in be ween he loops; he pi ch, which is he
dis ance be ween wo neighbou ing dwell poin s; and, he scan di ec ion, associa ed wi h
he mo emen o he beam wi hin he pa e n. In addi ion, he numbe o loops, pa e n
dimensions and geome y a e included. Finally, pa ame e s ela ed o he en i onmen al
condi ions such as he base p essu e, he ype o gas p ecu so and lux, he posi ion o
he GIS nozzle, he ype o subs a e, he empe a u e o he esidence ime o he
p ecu so molecules a e also decisi e a iables o he ab ica ion o nano-objec s.
Wi h he goal o lea ning how hese pa ame e s a ec he g ow h ope a ion and
handle hem, he dissocia ion p ocess caused by he elec on beam dese es special
a en ion. Among he many dis inc elec on-molecule in e ac ion p ocesses [7], he
Tuning he g ow h o 3D nanowi es by FEBID
97
elas ic sca e ing, ib a ional and elec onic exci a ion, dissocia i e elec on a achmen ,
neu al and bipola dissocia ion, and dissocia i e ioniza ion can be men ioned. In ligh o
his si ua ion, i may be hough ha he beam-molecule in e ac ion is oo complex o
ha e a ho ough knowledge and comp ehension o he mechanism a molecula scale. In
ac , ew expe imen al [8] and heo e ical s udies [9] in his ega d a e epo ed in
li e a u e. Howe e , unsophis ica ed simula ions o he ab ica ion p ocess by con inuum
models and app oaches o g ow h geome ies by Mon e Ca lo me hod ha e been al eady
conside ed o cla i y he in icacies o he FEBID g ow h p ocess [10].
To shed ligh on his opic, he single p ecu so species con inuum model o FEBID
should be con empla ed. This model conside s a weak p ecu so -subs a e in e ac ion and
neglec s he in e play be ween he adso bed p ecu so gas molecules. Fi s ly, Langmui
adso p ion whe e he su ace co e age is desc ibed as a unc ion o he p ecu so
adso ba e densi y, , is assumed. Secondly, an a e age esidence ime, , o he p ecu so
gas molecules on he subs a e su ace is aken in o accoun . Thi dly, he su ace di usion
phenomenon o he p ecu so gas molecules is also conside ed. Finally, he dissocia ion
induced by he elec on beam is modelled by a deple ion o  p opo ional o he
dissocia ion c oss-sec ion, 

, and he elec on lux dis ibu ion pe uni ime and a ea,
. Thus, he adially symme ic a e equa ion is w i en as ollows [11]:



,



=


1
−



,





−



,



+







,





+
1





,




−
(3.1)
−









,



1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

whe e he adso p ion, deso p ion, di usion and dissocia ion e ms can be sequen ially
iden i ied in he igh -hand side o he equa ion. In he adso p ion e m,  is he s icking
coe icien ,  he p ecu so lux, 

he comple e a ea densi y which co esponds o ha
o a monolaye , and 1− 

⁄ he ac ion o su ace si es a ailable o adso p ion. The
deso p ion e m de ines he adso ba e densi y pe  pe iod be o e deso p ion. The

Chap e 3
98
di usion e m deno es he sp eading o he p ecu so gas molecules on he su ace and is
p opo ional o he di usion cons an , . Finally, he dissocia ion e m indica es he
educ ion o  assuming an ene gy-in eg a ed 

and a adially symme ic  wi h he
Gaussian shape:




=


⁄
2


exp
$
−


2

%
(3.2)
whe e  is he elec on beam cu en ,  he elec on cha ge, he s anda d de ia ion and
 he adial pa ame e .
Addi ionally, he local deposi ion g ow h a e ℛ can be de ined as:
ℛ



=
'







(
)



,


*
+
,
-
(3.3)
whe e ' is he non- ola ile deposi ed p oduc a isen om a p ecu so gas molecule and

(
he dwell ime. Neglec ing he di usion e m —which can be a good app oach o a
wide ange o  and 
(
alues [1]—, he analy ical solu ion o Equa ion 3.3 can be
ob ained:
ℛ
=
'





.
1
/
0
−
1
/

1
1
−
exp

−
/


(

/


(
+

/


(3.4)
whe e /

is he deple ion a e and /
0
he eplenishmen a e:
/

=



+
1

+



(3.5)
/
0
=



+
1

(3.6)
A ough in e p e a ion o he g ow h a e can be ob ained as a unc ion o 
(
. On he
one hand, o ela i ely small 
(
, — ypically on he o de o nanoseconds —, ℛ inc eases
Tuning he g ow h o 3D nanowi es by FEBID
99
as a unc ion o . This deposi ing scena io is he elec on-limi ed egime because he
g ow h is es ic ed by inabili y o he elec on beam o decompose all p ecu so
molecules. On he o he hand, in he case o la ge 
(
, he dissocia ion a e exceeds he
gas p ecu so eplenishmen a e, gi ing ise o he p ecu so -limi ed egime. The balance
be ween he a ailabili y o p ecu so molecules on he g ow h a ea and he elec on beam
cu en is e y impo an because i will de e mine whe he he g ow h occu s in he
p ecu so -limi ed egime o he elec on-limi ed egime, which will a ec no only he
g ow h a e bu also he composi ion o he nanowi e [12]. Fu he mo e, when he mal
hea ing o he g owing deposi occu s, as p e iously ound in FEBID
[13][14][15][16][17], he decomposi ion o he p ecu so gas molecules will be mo e
e icien i empe a u es close o he he mal decomposi ion o he p ecu so a e eached.
These concep s a e o u mos impo ance o de e mining he app op ia e condi ions, i.e.,
he ideal alue o each pa ame e , o ensu e an e icien decomposi ion p ocess.
The gene al no ion o he heo y p esen ed he e can be applied o he ab ica ion o
any ype o s uc u e and o e s a s a ing poin o begin wo king. Howe e , al hough his
b ings a global o e iew, gi en he mul i ude o nanos uc u es shapes and ma e ials, he
op imiza ion p ocess o he speci ic a iables is essen ial o ind ou he bes esul s.
3.2 Tailo ing he undamen al p ope ies o 3D cobal nanowi es
Many ypes o ma e ials aise g ea in e es o hei s udy a he nanoscale. Fo
ins ance, hin- ilm laye s and mul ilaye s based on magne ic ma e ials ha e nowadays
a ious applica ions in he ields o da a s o age and sensing, one example o his being
he ha d disks [18][19]. E en so, indi idual magne ic nano-objec s a e also being
in es iga ed and engage huge a en ion due o hei g ea po en ial in applica ions such as
senso s [20], memo ies [21] and logics [22]. In his case, mos o he app oaches o hei
ab ica ion ely on s anda d li hog aphy p ocedu es, mos adequa e o pa e ning 2D
s uc u es on o magne ic hin ilms and mul ilaye s. Howe e , he e is an inc easing
Chap e 3
100
in e es on he ab ica ion o 3D magne ic nanos uc u es. In his ega d, FEBID is one
o he echniques ha allow add essing he g ow h o such 3D s uc u es
[23][24][25][26][27], pa icula ly hose based on magne ic ma e ials [28][29][30][31]
[32][33][34][35][36][37].
The use o p ecu so gas molecules con aining magne ic elemen s such as Co, Fe
and Ni pe mi s he g ow h o magne ic deposi s [28][38][39][40][41][42][43][44]. A
la ge de elopmen has been made owa ds he g ow h o magne ic deposi s wi h high
me al con en , high magne iza ion, high esolu ion and complex shapes, as ecen ly
e iewed [45][46]. Such de elopmen has been ocused on he op imiza ion o hin in-
plane magne ic laye s, whe eas limi ed wo k has been done in he case o 3D magne ic
deposi s. Howe e , he e a e many p omising applica ions o 3D magne ic deposi s in
scanning p obe echniques, such as MFM [34] and Fe omagne ic Resonance Fo ce
Mic oscopy [47], ace ack- ype magne ic memo ies [31], Hall senso s [48][49],
nanomagne ic logic ci cui s [34][50], supe conduc ing o ex la ice pinning [51], emo e
magne o-mechanical ac ua ion [37], e c. 3D ab ica ion implies he unde s anding o
speci ic g ow h phenomena which do no happen in he case o 2D deposi s, and as a
esul new in e p e a ion eme ges om he nano ab ica ion p ocess.
P e ious wo k on he g ow h o 3D nanowi es by FEBID has shown he ele ance
o se e al pa ame e s ha should be aken in o accoun . Fo example, he use o sub-nA
elec on beam cu en s p oduced by ield-emission guns is manda o y o he g ow h o
na ow nanowi es (<100 nm in diame e ) [31][52]. Mo eo e , he mal e ec s can be o
emendous impo ance in 3D nanos uc u es gi en ha p ecu so eplenishmen in he
a ea o g ow h occu s a a lowe a e compa ed o in-plane deposi s because he di usion
mechanism o p ecu so gas molecules om he subs a e will be weakened as he deposi
g ows in heigh . When g owing a 3D nanowi e, he subs a e su ace close o he g ow h
poin is small and he numbe o p ecu so gas molecules adso bed o be decomposed is
lowe han in 2D deposi s. In addi ion, since hea dissipa ion is di icul , he empe a u e
Tuning he g ow h o 3D nanowi es by FEBID
101
inc eases in he g ow h poin and can gi e ise o in e es ing e ec s such as g ow h egime
ansi ions, discussed in he nex subsec ions.
In his con ex , he impac o he mos ele an g ow h pa ame e s on he speci ic
p ope ies o 3D e omagne ic nanos uc u es and hei inal pe o mance will be
explo ed in his sec ion. The ocus is pu on he cha ac e iza ion o he ob ained
nanowi e’s diame e , composi ion and magne iza ion, wi h he aim o g owing na ow
nanowi es (<100 nm in diame e ), wi h high Co con en (>80% a .) and magne iza ion
app oaching he bulk alue.
3.2.1 Expe imen al de ails
The nanowi es we e ab ica ed in he comme cial Helios Nanolab 600 and 650 Dual
Beam equipmen using Co
2
(CO)
8
as a gas p ecu so . The subs a es we e TEM Cu g ids.
Co deposi s we e g own wi h low elec on beam cu en s (≤100 pA). The ol age was
ixed o 5 kV gi en ha p elimina y expe imen s did no lead o signi ican changes in
he composi ion om 5 kV o 30 kV. The nanowi es we e g own in spo mode, whe e
he elec on beam is con inuously i adia ing a single poin . A base chambe p essu e o
~1 × 10
-6
mba was achie ed be o e he injec ion o he p ecu so , wi h he GIS needle
posi ion a ~50 µm in 2, 3 and 4 di ec ions. The p ecu so gas lux was uned ia a manual
al e, which pe mi s o a y he chambe p essu e up o ~4 × 10
-5
mba . E en hough he
p ecu so gas lux canno be measu ed di ec ly, gi en i s linea ela ionship wi h he
chambe p essu e inc ease du ing gas injec ion, Δ6, and he p ecu so gas lux, , s a ed
as ∝Δ6 [53], moni o iza ion o he chambe p essu e du ing g ow h allows o es ablish
ela i e co ela ions wi h he physical p ope ies o he 3D nanowi es.
Some o he EDS expe imen s we e pe o med in he Helios Nanolab 650 Dual
Beam, using an exci a ion elec on beam ol age o 5 kV and beam cu en o 800 pA.
O he EDS expe imen s we e ca ied ou in an FEI Tecnai F30 TEM ope a ed a 300 kV.
EELS expe imen s we e pe o med in he FEI Tecnai F30 TEM and in a p obe-co ec ed
Chap e 3
108
Al hough speci ic expe imen s and/o simula ions could shed mo e ligh on he
o igin o his change in composi ion, om gene al a gumen s i can be s a ed ha a lowe
p ecu so gas lux he Co con en diminishes due o decomposi ion o esidual
con aminan species in he wo king chambe , mainly C and O. Also, he beha iou o he
Co con en as a unc ion o Δ6 esembles ha obse ed in in-plane deposi s [49]: an
op imum p ecu so lux window (1 × 10
-5
mba < Δ6 < 1.5 × 10
-5
mba ) exis s, whe e he
Co con en is ela i ely high. On he o he hand, a highe p ecu so gas lux he Co
con en is educed because incomple ely decomposed p ecu so gas molecules a e
inco po a ed o he deposi . The numbe o p ecu so gas molecules is so high ha he
elec on beam canno p ope ly dissocia e he gas. The di e en o igin o he dec eased
Co con en a low and high p ecu so lux can be also no ed in he C/O a io, which is
smalle han 1 a high p ecu so gas lux and la ge han 1 a low p ecu so gas lux. F om
Figu e 3.4, unde his g ow h condi ions, i is clea ha op imum Co con en (>85% a .)
can be only achie ed in he adial egime, whe e he diame e is a leas ~120 nm.
The ine icien decomposi ion phenomenon has also been ound in he expe imen
ep esen ed in Figu e 3.5. To e idence clea ly his e ec , STEM-EELS chemical maps
and p o iles we e acqui ed in a nanowi e g own in he adial egime unde he app op ia e
condi ions o induce he phenomenon. As illus a ed, a Co con en dec ease is exhibi ed
in he co e cen e. This en ails a ela i e C composi ion inc ease in ha a ea, so he
uni o m composi ion disappea s comple ely. I could be hough ha he cen al pa o
he nanowi e is so hick ha EELS signals a e no quan i ied p ope ly due o mul iple
sca e ing [55]. Howe e , he dec ease o in ensi y in he co e egion obse ed in he
HAADF-STEM image o he c oss sec ion, shown in he ounded inse o Figu e 3.5, can
only be explained by a educ ion o he a e age a omic numbe in his egion, hus a
educ ion o he Co con en .

Tuning he g ow h o 3D nanowi es by FEBID
109
Figu e 3.5. Rela i e composi ion p o iles as a unc ion o he adius o he nanowi e
de e mined by STEM-EELS. The inse depic s he HAADF-STEM image o a c oss-sec ion
in g ey scale, and he chemical maps showing he spa ial dis ibu ion o Co, C and O in g een,
blue and ed, espec i ely. Unde ined scale ba s a e 25 nm in he STEM image and 100 nm
in he STEM-EELS maps.
This is in good ag eemen wi h p e ious s udies sugges ions, whe e he Co signal
dec ease could be induced by a lack o p ecu so gas molecules due o a empe a u e
inc ease, caused by he cons an impac o he p ima y elec ons [56][57]. A highe
empe a u e leads o a dec ease in  and he p ecu so deso bs as e . By his, he ma e ial
deposi ed in he cen e o he nanowi e a e esidual componen s, basically C a oms wi h
a sligh con ibu ion o O ones. On he con a y, he olume a ound he co e cen e mainly
g ows hanks o SE emission, and i con ains a highe me allic con en due o i s lowe
empe a u e. This is eminiscen o he basics ela ed o a ecen publica ion o he
Chap e 3
110
g ow h o e ical hollow nanowi es by He
+
Focused Ion Beam Induced Deposi ion
(FIBID) [58].
Since he decomposi ion o he p ecu so gas molecules is closely linked o he
elec on beam p ope ies, he elec on beam cu en appea s o be a c i ical g ow h ac o .
As a i s app oxima ion, le us ocus he a en ion on nanowi es wi h jus one single
g ow h mode. As p e iously men ioned, a low elec on beam cu en is a p e- equisi e
o he g ow h o small-diame e nanowi es. This is ypically p oduced by using small
ape u es which limi he elec on beam size o he ab ica ion p ocess and, in his case,
because o he inhe en Co
2
(CO)
8
p ope ies. Fo example, he esul s ob ained o he
Fe
2
(CO)
9
p ecu so gas a e comple ely di e en , whe e he me allic composi ion is
cons an o all he a ailable elec on beam cu en s. In his scena io, i is impo an o
assess he e olu ion o all he composi ional elemen s in he esul ing 3D Co-FEBID
nanos uc u es as a unc ion o he elec on beam cu en . Figu e 3.6 shows Co, C and O
con en s e alua ed as a unc ion o he elec on beam cu en . An inc ease o he elec on
beam cu en p o okes an inc emen o he me allic composi ion. This ac ein o ces he
idea ha a comp omise in he elec on beam cu en ega ding he la e al dimensions and
he me allic composi ion mus be made.
Figu e 3.6. Rela i e composi ion as a unc ion o he elec on beam cu en o Co nanowi es.
Tuning he g ow h o 3D nanowi es by FEBID
111
In his line, dedica ed expe imen s ha e been ca ied ou using he bes g ow h
condi ions o ob ain he highes possible me allic con en a each pa icula alue o he
nanowi e diame e . The esul s a e summa ized in Figu e 3.7, whe e he Co con en is
ep esen ed as a unc ion o he diame e o op imum g ow h condi ions. The speci ic
g ow h pa ame e s o each nanowi e a e displayed in Table 3.2.
Figu e 3.7 indica es ha a high Co con en (>85% a .) can be achie ed in nanowi es
wi h diame e la ge han ~120 nm, which co espond o he adial egime. Howe e , he
Co con en in he nanowi es wi h linea egime, whose diame e is smalle han ~80 nm,
s a s om ~75% a . o diame e s o ~80 nm and diminishes quickly as he diame e is
educed. Fo ins ance, o diame e s o ~60 nm he Co con en is only ~45% a . Gi en
ha he nanowi es p esen ypical oxidized shells o a ound 5 nm [52][59], he measu ed
a e age Co con en will be lowe as he wi e diame e dec eases. This means ha in he
co e o he nanowi e he Co con en is expec ed o be highe han he a e age alue, his
e ec being mo e signi ican o he na owes nanowi es.
Figu e 3.7. Co composi ion as a unc ion o he nanowi e diame e o op imized g ow h
condi ions a each pa icula alue o he diame e .
Chap e 3
112
Diame e
(nm)
Co composi ion
(%, a .) Technique G ow h cu en
(pA)
8
P (10
-6
mba )
56.9 40.6 EDS 50 2.8
58.8 46.9 EDS 25 10.3
60.4 43.1 EDS 50 10.2
65.0 58.3 EDS 100 10.5
65.6 50.0 EDS 100 9.3
73.7 67.3 EDS 100 8.1
79.1 81.2 EDS 50 6.9
80.9 67.5 EDS 100 8.1
81.2 83.8 EDS 100 8.4
82.6 84.0 EDS 50 7.8
119.2 83.1 EELS 50 2.8
123.9 87.4 EDS 50 5.2
148.5 83.2 EDS 100 6.9
149.0 87.4 EELS 100 6.1
Table 3.2. Da a associa ed wi h he in o ma ion ep esen ed in Figu e 3.7: diame e , Co
con en and echnique used o ob ain i , elec on beam cu en and Δ6 du ing g ow h. A
ypical e o o ~2% a . in composi ion is conside ed assuming uni o m dis ibu ion.
3.2.4 Magne ic induc ion as a unc ion o he diame e
In o de o co ela e he Co con en o he nanowi es wi h hei magne iza ion, EH
expe imen s ha e been ca ied ou . Th ee nanowi es which con ain di e en me allic
composi ions and g ow h modes ha e been analysed o ob ain quan i a i e alues o he
magne ic induc ion.
By using Equa ion A.3, he a e age magne ic induc ion inside he nanowi e along
i s long axis, deno ed simply as 9 he ea e , can be calcula ed. In Figu e 3.8, he esul s
co esponding o h ee nanowi es, ep esen a i e o he h ee di e en egimes ound, a e
shown.
Tuning he g ow h o 3D nanowi es by FEBID
113
Figu e 3.8. (a) Magne ic induc ion lux lines o nanowi es wi h Co con en o (a) 87.4% a .
(NW1), (b) 67.5% a . (NW2), and (c) 40.6% a . (NW3), all ob ained om he magne ic phase
image a e no malizing by he maximum hickness and pe o ming he cosine o 700 imes
he magne ic phase shi image. (d) T ans e sal p o iles o 9 o NW1, NW2 and NW3.
The alues ob ained o 9 close o he nanowi es’ su aces a e no eliable due o he
unce ain ies in he sample hickness a hose posi ions and edge e ec s a he oxidized
nanowi e su ace. Fo his eason, he alues o 9 ob ained a he edges o he nanowi es
a e masked wi h a semi- anspa en band, whe eas only he alues ob ained in he cen al
pa o he nanowi es a e us wo hy. The nanowi e wi h he la ges diame e , 123.9 nm,
co esponding o he adial egime, p esen s a 9 (~1.33 T) no a om he bulk alue,

Chap e 3
114
1.76 T. This high alue o he magne iza ion co ela es well wi h he high Co con en in
he nanowi e, 87.4% a . A second nanowi e, co esponding o he in e media e linea and
adial egime, has been analysed a he base, in he sec ion g own unde linea egime. I
p esen s a 9 o 0.78 T, a ound 50% o he bulk magne iza ion o Co. This educ ion is
expec ed gi en he educed Co con en (67.5% a .) in his nanowi e. A hi d nanowi e,
co esponding o he linea egime, p esen s a lowe 9 (~0.41 T), which can be expec ed
gi en i s e en lowe Co con en (40.6% a .).
3.2.5 Discussion o he esul s
I can be a gued ha FEBID g ow h o unc ional magne ic nanos uc u es equi es
exhaus i e con ol o a high numbe o g ow h pa ame e s. Thei p ecise uning can be
c ucial in pa icula cases, such as he g ow h o 3D Co nanowi es discussed in his
sec ion. In he p ocess o g ow h op imiza ion, a numbe o in e es ing phenomena ha
should be aken in o accoun o hei p ac ical applica ion ha e been encoun e ed.
The i s impo an inding ega ds he exis ence o wo g ow h modes wi h di e en
physical p ope ies, deno ed linea and adial egimes due o ce ain simila i ies wi h
epo ed g ow h o 3D Fe nanowi es [13]. In he adial egime, he nanowi es ea u e
diame e s >120 nm wi h e y high Co con en s (>85% a .), showing a high magne iza ion
no a om he bulk alue (1.76 T). In he linea egime, he diame e s a e ypically
lowe han 80 nm wi h he Co con en s ongly diminishing o dec easing diame e . Fo
ins ance, 9 is a ound 1/2 o he bulk alue o nanowi es wi h ~80 nm in diame e and
~75% a . Co, educing 9 down o 1/4 o he bulk alue o nanowi es wi h ~60 nm in
diame e and ~45% a . Co. I canno be disca ded ha he nanowi es o low Co con en
ha e a eas wi h inhomogeneous composi ion, wi h he iche Co egions con ibu ing
mo e o he magne iza ion o he nanowi e. In e es ingly, inside he same nanowi e, a
ansi ion be ween bo h g ow h modes can be obse ed in a ce ain ange o g ow h
pa ame e s. This e ec seems o indica e ha he mal deso p ion and di usion e ec s
Tuning he g ow h o 3D nanowi es by FEBID
115
du ing he g ow h may play a key ole. The capaci y o dissipa e he hea o igina ed by
he elec on beam is educed as he nanowi e g ows in heigh , being he ip g owing
p og essi ely u he away om he subs a e. A a ce ain heigh , he e is an o e hea ing
which could esul in a change o he g ow h mode. Recen esul s, published a e ou
wo k had inished, highligh his e ec and p o ide a quan i a i e desc ip ion [17]. The
exis ence o such single nanowi es wi h wo diame e s seems use ul o s udies o
magne ic-domain-wall p opaga ion, gi en he endency o domain walls o ge pinned a
he loca ion o he ansi ion be ween bo h diame e s [60].
The co ela ion ound be ween he diame e o he nanowi e and i s composi ion is
impo an gi en he ela ionship obse ed be ween he Co con en and he magne iza ion
o he nanowi e. I a nanowi e wi h 9 close o he bulk alue is equi ed, he bes op ion
is o g ow a nanowi e wi h diame e o a leas 120 nm. Howe e , in many p ac ical
si ua ions, na ow nanowi es (<100 nm) a e eques ed, in which case a maximum Co
con en o ~80% a . can be achie ed. In such si ua ion, 9 is obse ed o dec ease wi h
espec o he bulk alue. The e a e many po en ial applica ions o hese nanowi es such
as magne ic unc ionaliza ion o can ile e s [61][28][34][62][30], 3D logic s uc u es
[34][50], cylind ical condui s o domain-wall p opaga ion [31], e c. whe e la e al
esolu ion is mo e impo an han he absolu e alue o he magne iza ion. In hose cases,
he ype o nanowi es g own he e in he linea egime mee he equi ed physical
p ope ies. Jus as a pa icula example, he Fe magne ic ods used in he pas by F anken
e al. had 9 o 0.13 T and we e able o pin domain walls in a domain-wall condui [33].
3.3 Elec ically-biased pa e ned me al s uc u e
In spi e o wha has been p esen ed in he p e ious sec ion, FEBID s ill p esen s
some limi a ions wi h espec o he p ecise con ol o he dimensions o nano-objec s as
well as i s use on insula ing subs a es. To o e come hese limi a ions, in his sec ion a
no el app oach based on he use o elec ically-biased me al s uc u es pa e ned on he
Chap e 3
116
su ace o he subs a e is explo ed, called he ARAGON-Chip (ac onym de i ed om
ARchi ec u al Adjus men by G id O e lay Nano echnology-Chip) [63]. He ea e , his
e e s o any ype o insula ing subs a e op-co e ed wi h a pe iodically pa e ned me al
laye .
3.3.1 In oduc ion
One o he p ominen p ope ies sea ched by any li hog aphy echnique is he
capabili y o be used on an a bi a y subs a e. In he case o li hog aphy echniques based
on cha ged pa icles, such as EBL and FIB li hog aphy, a limi ing ac o is he di icul y
o wo king on insula ing subs a es [64][65]. The building o elec ic ields in he icini y
o an insula ing subs a e (due o cha ging e ec s) p oduces unwan ed beam de lec ions
ha uin he esolu ion o e en impede hei p ac ical applica ion [66][67][68]. In he case
o EBL, he p oblem can be ci cum en ed by wo king unde c i ical-ene gy condi ions
[69], using a iable-p essu e EBL [70], o including addi ional s eps in he p ocess, like
he e apo a ion o a me al laye on op o he esis ha is subsequen ly e ched away [71].
In he case o FIB, i has been ound ha using elec on i adia ion simul aneously is
help ul owa ds cha ge minimiza ion [72].
FEBID is ano he cha ged-pa icle nanoli hog aphy echnique su e ing om he
same p oblem when applied on insula ing subs a es. In gene al, FEBID applica ions a e
de eloped using subs a es allowing he cha ge dissipa ion and he a oidance o
de imen al elec ic po en ials in he p oximi y o he subs a e su ace. In ac , i has
ecen ly shown ha he use o an insula ing subs a e (such as polyca bona e) hampe s
he g ow h o high- esolu ion nanos uc u es by FEBID unless pads o cha ge dissipa ion
exis on he subs a e, close o he a ea o g ow h [73].
In his hesis, he s a egy ollowed o o e come he cha ging p oblem o FEBID
consis s on he use o pa e ned me al s uc u es ab ica ed by op ical li hog aphy, which
could also be p oduced by any o he li hog aphy echnique. Mo eo e , i he pa e ned
Tuning he g ow h o 3D nanowi es by FEBID
117
me al s uc u e on an insula ing subs a e is elec ically biased, unable elec ic ields can
be c ea ed on he subs a e su ace, p oducing a emendous impac on he ajec o ies o
he p ima y elec ons and he gene a ed SE. He ea e , i will be shown ha his new
deg ee o eedom in FEBID is use ul o une he dimensions o 3D nanos uc u es g own
by his echnique. A p e ious p oo -o -concep wo k has shown ha an elec ic ield
p oduced by a con inuous me allic subs a e can modi y he dimensions o FEBID
deposi s g own on i s su ace [74]. Also, local elec ic ields ha e been p e iously used
o ailo he g ow h o nanowi es using echniques such as VLS p ocesses [75], esul ing
in a lexible me hod o une hei dimensions. Howe e , in his case he in e es is ocused
on pa e ned me al s uc u es wi h mic ome ic holes, which allows he local applica ion
o unable high elec ic ields inside he holes.
Finally, elec on beam de ocus will be used as a new ool o modula e he diame e
and leng h o 3D nanowi es. Al hough he dimension b oadening e ec o beam de ocus
has al eady been epo ed in FEBID [76], in si u con ol o his pa ame e o ob ain 3D
s uc u es wi h ailo ed a ying diame e s ep esen s a new a enue in he use o FEBID
o he g ow h o unc ional magne ic, supe conduc ing o pho onic ma e ials.
3.3.2 Expe imen al de ails
Pa e ned me al s uc u es we e ab ica ed on SiO
2
, MgO and qua z subs a es by
op ical li hog aphy. Fi s ly, he elec on-beam-e apo a o equipmen was used o deposi
wo consecu i e me allic laye s: a C laye wi h ~10 nm in hickness o imp o e he
adhe ence and a Cu laye o ~500 nm. The chambe base p essu e was 4 × 10
-7
mba ,
inc easing up o 1 × 10
-6
mba in he C deposi ion, using a cu en o 20 mA o 105
seconds. The p essu e o he Cu deposi ion was 1.5 × 10
-6
mba a 25 mA o 18 minu es.
A e ha , a s anda d li hog aphy p ocedu e was ollowed using a posi i e esis and a
mask wi h a pe iodic a ay o holes, so he me allic ilm was pe o a ed wi h ci cula
holes wi h a diame e o ~4 µm, as shown in Figu e 3.9.
Chap e 3
124
The ec o map o he elec ic ield in he 23 plane o Figu e 3.11 is displayed in
Figu e 3.13(a), which illus a es ha he applica ion o a nega i e (posi i e) DC ol age
in such s uc u e p oduces la ge and highly di ec ional elec ic ields poin ing owa ds
(o om) he cen e o he hole. In he cen e o he hole, he elec ic ield anishes. The
o al elec ic ield in he plane pe pendicula o he hole, 24 plane in Figu e 3.11,
co esponds o he ec o map shown in Figu e 3.13(b). The elec ic ield is e y small
along he symme y axis o he ci cula hole and g ows apidly as he dis ance om his
axis inc eases.
The elec ic ield nume ical calcula ions and ec o maps ep esen a ions we e
pe o med by D . So aya Sangiao.
3.3.5 Dimensional modula ion as a unc ion o he applied ol age
I has been obse ed ha he g ow h o he nanowi es unde di e en ol age alues
applied o he ARAGON-Chip, whils keeping he o he g ow h condi ions cons an ,
a ec s d ama ically he dimensions o he nanowi es. In hese expe imen s, P -C and W-
C nanowi es a e g own a he cen e o he holes wi h amo phous SiO
2
subs a e unde
di e en ol ages in he ange o -200 V o +200 V.
On he one hand, as shown in Figu e 3.14(a), he nanowi e diame e is ound o
change om a la ge alue a ound 100 nm unde -200 V o a minimum alue o 50 nm a
-25 V, and hen inc easing up o 90 nm unde +200 V. This igu e illus a es he uning
o he alue o he nanowi e diame e by a ac o o 2 by applica ion o he c ea ed local
elec ic ields. On he o he hand, he aspec a io o he nanowi e is also ep esen ed in
Figu e 3.14(a). I shows a maximum alue a a ound -25 V, in good co espondence wi h
he minimum alue o he diame e a such ol age, and indica es ha he aspec a io
inc eases by a ac o o 4 wo king unde such ol age in compa ison o -200 V. SEM
images o P -C nanowi es g own espec i ely unde -100 V, -35 V and +100 V a e shown
in Figu e 3.14(b-d). A -100 V he diame e a a heigh o 1 µm is 73 nm, whe eas i

Tuning he g ow h o 3D nanowi es by FEBID
125
dec eases o 50 nm unde -35 V and inc eases again o 83 nm unde +100 V. Mo eo e ,
he nanowi e leng h is, espec i ely o hose ol ages, 2.6 µm (-100 V), 2.9 µm (-35 V)
and 2.2 µm (+100 V), co esponding o linea g ow h a es o 43.3 nm/s, 48.3 nm/s and
36.7 nm/s, espec i ely. Thus, he esul s a e conclusi e wi h espec o an op imized
nanowi e g ow h in e ms o esolu ion unde nega i e ol ages a ound -25 V.
Figu e 3.14. Dimensional modula ion o P -C nanowi es g own o 60 seconds on amo phous
SiO
2
subs a e: (a) dependence o he diame e and he aspec a io wi h he ol age applied
o he ARAGON-Chip. SEM a i icially colou ed images o selec ed nanowi es g own unde
(b) -100 V, (c) -35 V and (d) +100 V, ma ching he poin s ma ked wi h g een a ows in (a).
Chap e 3
126
Simila expe imen s ha e been ca ied ou o in es iga e he in luence o local
elec ic ields on he dimensions o W-C nanowi es using he ARAGON-Chip on he
same amo phous SiO
2
subs a e. As shown in Figu e 3.15, he minimum nanowi e
diame e (~65 nm) occu s in he -25 V o -50 V ange and he aspec a io is maximized
in he same ol age ange. In his case, he deg ee o unabili y o he diame e and he
aspec a io compa ed o he P -C case is lowe bu subs an ial ( ac o s o 1.3 and 1.7,
espec i ely).
In iew o he se o esul s ob ained o P -C and W-C nanowi es, spa ially-
dependen elec ic ields can be es ablished as a new deg ee o eedom o une he
dimensions o nanowi es g own by he FEBID echnique using his no el app oach. The
o igin o he e ec will be discussed he ea e in he ligh o he physical phenomena
in ol ed in he FEBID g ow h and he elec ic ield dis ibu ion in he ARAGON-Chip.
Figu e 3.15. Dimensional modula ion o W-C nanowi es g own on amo phous SiO
2
subs a e
illus a ing he dependence o hei diame e and aspec a io wi h he ol age applied o he
ARAGON-Chip.
Tuning he g ow h o 3D nanowi es by FEBID
127
3.3.6 Quali a i e discussion o he elec ic ield ac ion
Rega ding he physical phenomena in ol ed in he g ow h o e ical s uc u es by
FEBID, Fowlkes e al. no ed ha he mos signi ican con ibu ion o he dissocia ion o
he p ecu so gas molecules a ises om he p ima y beam elec ons and hei gene a ed
seconda y elec ons (SE-I), wi h lowe ele ance om BSE and hei gene a ed
seconda y elec ons (SE-II) [80]. La e , Smi h e al. s essed he impo an ole played by
o wa d-sca e ed elec ons (FSE) in he g ow h o 3D nanowi es as well as he
dependence o he e ec wi h he p ima y beam ene gy and he esul ing g ow h egime
[81]. Mo eo e , A nold e al. showed ha SE-II a e esponsible o he halo deposi
a ound he main deposi in 2D s uc u es, a ec ing he inal deposi esolu ion [82]. A
simila s udy by Schmied e al. in he case o 3D deposi s has shown a ious compe ing
e ec s, wi h signi ican b oadening o he deposi wid h unde in e media e o low
elec on beam ene gy [83]. The FEBID p ocess is hus complex and depends on many
pa ame e s, bu in gene al he p ecu so dissocia ion p ocess is de e mined by high-
ene gy elec ons (mainly a ising om p ima y beam elec ons and FSE) as well as by
low-ene gy elec ons (mainly SE-I and SE-II). The e o e, ou expe imen al inding o a
conside able e ec o local elec ic ields on he dimensions o FEBID deposi s should
be co ela ed wi h he e ec p oduced by such elec ic ields on he ajec o ies o hese
elec ons esponsible o he p ecu so gas molecules dissocia ion.
In conside a ion o he p e iously epo ed esul s, a quali a i e explana ion o he
obse ed e ec can be p o ided. F om he elec os a ic poin o iew, he elec ic ield
dis ibu ion gene a ed a he pe o a ed Cu ilm is in ac ac ing as a small (de) ocusing
lens. The elec os a ic lenses can be ound in elec on and ion mic oscopes [84], and o he
de ices based on cha ged pa icles [85]. In he ARAGON-Chip, as he p ima y elec on
beam app oaches he pe o a ed cha ged ilm, i su e s a de ia ion owa ds he op ical
axis (unde nega i e ol age) o o he op ical axis (unde posi i e ol age), as ske ched
in Figu e 3.16. In bo h cases, his e ec i ely leads o an elec on beam de ocus.
Chap e 3
128
Figu e 3.16. Ske ch illus a ing he ele an phenomena in ol ed in he g ow h o 3D
nanowi es by FEBID when an ex e nal posi i e o nega i e ol age is applied o he
ARAGON-Chip. On he one hand, he p ima y beam becomes sligh ly de ocused, gi ing ise
o he diame e b oadening. On he o he hand, he SE a e s ongly a ac ed o ('
Z[
0) o
epelled om ('
Z[
]0) he op ical axis, con ibu ing o he nanowi e na owing o
b oadening, espec i ely.
As epo ed by Plank e al. [76], he e ec o de ocusing he p ima y elec on beam
igge s an inc ease o he nanowi e diame e . On he o he hand, he high elec ic ield
will s ongly modi y he ajec o y o he SE p oduced in he subs a e and he g owing
s uc u e, which is also c ucial o he FEBID g ow h.
Due o he low ene gy o SE-I and SE-II (<50 eV) [86], hey will unde go s ong
a ac ion o o epulsion om he op ical axis o nega i e o posi i e ol age,
Tuning he g ow h o 3D nanowi es by FEBID
129
espec i ely. In ac , simila ol age alues in he ange o a ew ens o hund eds o ol s
a e ac ually used in elec on mic oscopes o op imize he imaging con as by SE, whe e
biasing ol age can be applied o he sample i sel [87][88] o o he elec on de ec o
[89][90]. As a esul , combining he g ow h by FEBID and he ARAGON-Chip s a egy,
he use o a nega i e ol age will push SE-I and SE-II o he hole cen e con ibu ing o
dec ease he nanowi e diame e , whe eas he use o a posi i e ol age makes SE-I and
SE-II o be pulled ou om he hole cen al axis leading o a diame e enla gemen .
Summa izing, when a nega i e ol age is applied o he pe o a ed Cu ilm, wo
e ec s will compe e: nanowi e na owing due o he e ec o he elec ic ield on he SE-
I and SE-II, and nanowi e b oadening due o he de ocusing e ec o he elec ic ield on
he p ima y beam elec ons. This ag ees wi h he expe imen al esul s shown in Figu e
3.14 and Figu e 3.15. S a ing om 0 V, he nanowi e diame e i s dec eases down o
an applied ol age o a ound -25 V, hen inc easing he hickness as he ol age is educed
o -200 V. As he ske ch in Figu e 3.16 also illus a es, his is he expec ed e olu ion
gi en he apid ocusing o he SE owa ds he hole cen al axis a low ol ages and he
smoo he inc ease o he p ima y beam diame e wi h he ol age. Finally, a posi i e
ol age, he diame e is always inc easing wi h ol age gi en ha bo h e ec s con ibu e
o he nanowi e b oadening.
3.3.7 Dimensional modula ion as a unc ion o he beam de ocus
In o de o e i y he hypo hesis desc ibed abo e, addi ional expe imen s we e
pe o med whe e he elec on beam ocus condi ions we e con ollably changed be o e
and du ing he nanowi e g ow h. Fo ha , he ocus heigh , 4, was a ied wi h espec o
he op imum ocus condi ion, (4=0), o in es iga e he co esponding changes in he
nanowi e diame e and heigh wi h he de ocus, ∆4.
The i s expe imen s consis ed o g owing P -C nanowi es o di e en 4 alues
ixed du ing he whole nanowi e g ow h. F om he op imum ocus condi ion, bo h

Chap e 3
130
o e ocus (4 0) and unde ocus (4>0) condi ions we e conside ed. In he i s case
he beam is ocused below he hole 23 plane, whe eas in he second one he beam is
ocused abo e i . The ob ained esul s o he alues o he diame e and aspec a io as a
unc ion o 4 a e ep esen ed in Figu e 3.17. In o de o check ha he b oadening e ec
is independen o he ol age applied o he ARAGON-Chip, he expe imen s we e
pe o med a -25 V and -200 V, ep esen ed in Figu e 3.17(a) and 3.17(b), espec i ely.
The 4 alue has been swep a maximum o 40 µm, leading o eno mous di e ences in he
nanowi e diame e and aspec a io. These a ia ions each a ac o o 3 o he diame e
and a ac o o 12 o he aspec a io wi h ∆4 o ~20 µm.
On he one hand, hese esul s highligh he impo ance o a good p ima y beam
ocus in o de o achie e he highes esolu ion in he g ow h o 3D nanos uc u es. In
o de o show he di e ences which appea in he SEM images when he 4 alue a ies,
an example is shown in Figu e 3.18. I can be app ecia ed he de ocusing e ec o a ∆4
o ~20 µm in compa ison wi h he op imum ocus posi ion o imaging acquisi ion. On
he o he hand, he esul s in e es ingly show an addi ional ing edien o play wi h du ing
he g ow h o 3D nanos uc u es by FEBID. To exploi his addi ional pa ame e , he 4
alue was a ied du ing he g ow h o single nanowi es in o de o c ea e con inuous
nanos uc u es wi h modula ed diame e . Fi s , as shown in Figu e 3.19(a), a P -C
nanowi e wi h la ge diame e (146 nm) s a s o g ow due o he p ima y beam de ocus
(∆4 o 20 µm). A 72 seconds, by b inging 4 in o he op imal posi ion wi h a quick (~1
second) change in he 4 posi ion, a na ow sec ion (64 nm in diame e ) s a s o g ow.
A e 72 seconds, he 4 posi ion is modi ied 20 µm, p oducing a p ima y beam de ocus
and he co esponding inc ease o he diame e o 119 nm. A e ano he 72 seconds in
hese condi ions, he g ow h is inished, ob aining a diame e -modula ed nanowi e wi h
wide-na ow-wide sec ions. A second diame e -modula ed nanowi e has been g own
ollowing a simila s a egy bu wi h na ow-wide-na ow sec ions, as shown in 3.19(b).
Tuning he g ow h o 3D nanowi es by FEBID
131
Figu e 3.17. Dimensional modula ion o P -C nanowi es g own o 60 seconds on amo phous
SiO
2
subs a e: dependence o he diame e a hal nanowi e’s heigh and aspec a io as a
unc ion o he p ima y beam ocus heigh . The ex e nal ol age applied o he ARAGON-
Chip was (a) -25 V and (b) -200 V.
Chap e 3
132
Figu e 3.18. SEM op iew images o a ∼4-
µ
m-diame e hole wi h a 3D P -FEBID nanowi e
g own on he amo phous SiO
2
subs a e, wi h he elec on beam ocused (a) 20 µm abo e he
heigh o he Cu su ace, (b) a he heigh o he Cu su ace and (c) 20 µm unde he heigh o
he Cu su ace. In all cases he e is no ol age applied o he ARAGON-Chip.
Figu e 3.19. Diame e -modula ed P -C a i icially colou ed nanowi es g own on SiO
2
subs a e by means o he in si u a ia ion o he p ima y elec on beam ocus condi ion. Each
hin and hick diame e egion was ab ica ed o 72 seconds.
Tuning he g ow h o 3D nanowi es by FEBID
133
I is in e es ing o men ion ha , despi e e e y sec ion in he nanowi es o Figu e 3.19
has been g own o 72 seconds, hei espec i e leng h is di e en . This is expec ed o
sec ions wi h dissimila diame e , whe e i would be expec ed he conse a ion o he
olume g ow h a e ins ead o he linea g ow h a e. Howe e , his leng h di e ence also
occu s o sec ions wi h he same diame e , as i can be clea ly obse ed in Figu e 3.19(b)
o he na ow sec ions. In his case, he op na ow sec ion is sho e han he bo om
one, which can be explained by he diminishmen o he g ow h a e wi h an inc easing
dis ance o he subs a e caused by p ecu so gas di usion e ec s [91].
I has been checked ha he nanowi e diame e inc eases as 4 mo es away om i s
op imum posi ion. In he ligh o his inding, inducing a ∆4 keeping he subs a e s ill
has he same e ec as mo ing he subs a e in he e ical axis when keeping 4 cons an .
Howe e , mechanical mo emen s o he s age make his la e app oach less e ined, hus
he diame e changes ha e been always ob ained in oducing a ∆4. So a , o a single
nanowi e g own unde a cons an 4, sligh changes in diame e along he leng h we e
de ec ed. Ne e heless, addi ional expe imen s we e ca ied ou g owing W-C nanowi es
and inducing diame e changes keeping he same 4 alue and subs a e posi ion du ing
he whole g ow h. Fo his pu pose, a u he s ep owa ds dimensional modula ion o 3D
nanowi es can be aken by using he imme sion imaging mode du ing g ow h.
In his mode, a magne ic ield is applied o collec a highe numbe o elec ons han
in s anda d ield- ee mode, ob aining ul a-high- esolu ion images. As shown in Figu e
3.20, his mode will be used o he ab ica ion o nanowi es. The nanos uc u es we e
g own a di e en posi ions o a s ill sloping subs a e unde he same ocus condi ion,
whe e jus he subs a e heigh changes o each case. The ed do ed line indica es he
cons an 4 alue used o he g ow h o he nanowi es. Figu e 3.20(a) illus a es he
nanowi e wi h he op imum ocus heigh a he g ow h s a ing poin . A smoo h
con inuous beam de ocus ∆4 is in oduced pe se du ing he g ow h o he nanos uc u e,
inc easing he diame e om 39 nm o 52 nm as he ocus is g adually d i en away.
Chap e 3
140
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Chap e 4: Towa ds p ope ies
imp o emen by he mal annealing
In his chap e , he mal annealing s a egies a e ollowed o o e come he Focused
Elec on Beam Induced Deposi ion de iciencies in e ms o pu i y and c ys allini y.
Di e en ex si u and in si u pos -g ow h ea men s we e pe o med in 3D Co and Fe
nanowi es o inc ease he me allic composi ion, induce a c ys alliza ion o he pseudo-
amo phous as-g own s uc u es and enhance he ne magne ic induc ion alues.
Dedica ed in si u TEM expe imen s we e ca ied ou o moni o in eal ime changes in
he nanowi es p ope ies as a unc ion o empe a u e and ime, shedding ligh on he
nanoscale p ocesses in ol ed du ing he annealing p ocedu e.

Chap e 4
146
4.1 In oduc ion
The FEBID ab ica ion p ocess implies he elec on-beam-induced decomposi ion
o a me al-o ganic p ecu so gas adso bed on he g ow h su ace, undamen ally d i en
by he SE emi ed by he subs a e o he nascen deposi ma e ial [1]. One o he main
issues o his syn he ic echnique is he exis ence o chemical impu i ies due o
incomple ely dissocia ed p ecu so gas molecules inco po a ed in o he deposi . In
addi ion, he s uc u es also con ain di e en le els o con aminan s o igina ing om he
dissocia ion o esidual gases in he wo king chambe [2]. Despi e his, as desc ibed in
Chap e 3, pu i y can be imp o ed by p ecise con ol o p ima y elec on beam
pa ame e s, chambe base p essu e, p ecu so gas lux, e c. [3], which in some cases
enables he ab ica ion o deposi s o high me allic con en [4][5][6][7][8]. Howe e , in
many cases he as-g own me allic con en o en emains mode a e [9]. Thus, he lack o
pu i y and he poo c ys allini y will in gene al be limi ing ac o s o capi alizing he ull
po en ial o FEBID.
To ace his limi a ion, di e se app oaches ha e been ollowed o inc ease he pu i y
o FEBID deposi s, as e iewed by Bo man e al. in 2009 [2], and u he explo ed since.
This includes in si u [10][11] and ex si u [12][13][14] pos -annealing ea men s a high
acuum and unde con olled eac i e gas a mosphe es [15][16], use o subs a es a high
empe a u es du ing g ow h [17][18], elec on beam i adia ion o he deposi s [19][20],
lase -assis ed hea ing du ing deposi ion [21][22], pos -g ow h Joule hea ing upon
injec ion o high elec ic cu en s [23], supe sonic je deli e y o p ecu so gas [24], use
o ca bon- ee p ecu so gases [25], and combina ions o all hese me hods
[16][26][27][28][29]. Fo example, as ounding success has been achie ed in g owing
i ually-pu e P deposi s by pos -g ow h elec on i adia ion in O a mosphe e [15], o
unc ional Au plasmonic nanos uc u es by elec on beam i adia ion in wa e apo
a mosphe e [30]. Howe e , such widely-used s a egies ha e been gene ally applied o
2D deposi s, whe eas pu i ica ion o 3D objec s ha e been sca cely a emp ed [31]. The
Towa ds p ope ies imp o emen by he mal annealing
147
la e p esen s speci ic p oblems: o ins ance, he a chi ec u e s abili y can be
comp omised due o he high- olume sh inkage occu ing in low me al con en deposi s,
e en ually leading o a subs an ial modi ica ion o he objec shape o e en he collapse
o he 3D s uc u es [32].
In ou case, a special emphasis should be gi en o magne ic ma e ials g own by
FEBID. Speci ically, Co- [33], Fe- [34] and Ni-based [35] p ecu so gases ha e been
used, in which low me allic con en esul s in deg aded magne ic p ope ies. As a esul ,
he unc ionali y o FEBID-g own magne ic de ices may be comp omised. Ne e heless,
unde op imum g ow h condi ions, Co and Fe deposi s a e amongs he FEBID ma e ials
wi h highes me allic con en le els (~95% a .) [5][36][37][38]. In bo h cases, as-g own
high pu i y 2D deposi s ha e been achie ed wi h limi ed la e al esolu ion and small
c ys alline size. In he case o 3D magne ic deposi s, he dispe sion o composi ion alues
ound in he li e a u e is high, gi en he s ong dependence o he g ow h mode o small
changes in he nume ous g ow h pa ame e s [37][39]. None heless, 3D nanos uc u es
wi h a high aspec a io, such as e ical nanowi es, e idence a d as ic educ ion o he
me allic con en o dec easing diame e . Mo eo e , he na u al oxida ion o he su ace
upon ai exposu e ( ypically 5-nm- hick) becomes c i ical as he su ace- o- olume a io
signi ican ly inc eases and impai s he e omagne ic p ope ies o he nanos uc u es due
o he o ma ion o non- e omagne ic species [40][41]. I is pa icula ly impo an o
emphasize ha he pu i y and c ys allini y will ha e g ea impac in he elec ical
anspo [10] and magne ic p ope ies (sa u a ion magne iza ion, magne oc ys alline
aniso opy, coe ci e ield, e c.) [39][42], bo h key o he po en ial applica ion o FEBID
magne ic deposi s. Fo all hese easons, pu i ica ion o 3D FEBID magne ic objec s is
an exci ing challenge and di e en me hods ha e been explo ed o e he yea s.
The i s a emp s o pu i y Fe deposi s we e ca ied ou by Shimojo e al. h ough
ex si u he mal annealing and elec on beam i adia ion in ul a-high acuum,
demons a ing he o ma ion o highly-magne ic α-Fe deposi s, in some cases coexis ing
Chap e 4
148
wi h Fe ca bides [13]. The same g oup subjec ed 3D nanos uc u es o pos annealing up
o 600 ºC, achie ing Fe con en s nea 60% a . [43]. S udies on FEBID Co include he
wo k by Belo a e al., who analyzed C-seeded mic ome ic deposi s g own on subs a es
a 70 ºC, on he e ge o he he mal decomposi ion o he p ecu so gas, which p esen ed
a me al con en >95% a . Co [44]. Begun e al. explo ed he ca aly ic ac i i y o Co in a
H
2
eac i e a mosphe e upon elec on beam i adia ion, obse ing he o ma ion o
me allic Co only in a 20-nm- hick su ace egion o he deposi [45]. The e ec o in ense
elec ic cu en on he p ope ies o suspended Co nanowi es has also been epo ed o
induce pu i ica ion om 80% o 89% a . Co and c ys alliza ion in o la ge ace-cen e ed-
cubic ( cc) c ys als caused by local Joule hea ing and elec omig a ion [23]. Recen ly,
pos -g ow h annealing in high acuum o hin Co s ipes inc eased i s composi ion om
67% o 84% a . Co, wi h a conduc i i y o me allic beha io and h ee o de s o
magni ude highe han ha o he as-g own ma e ial [10].
Such p e ious wo k has p o ided hin s on how o imp o e he pu i y and
c ys allini y o magne ic deposi s g own by FEBID. This chap e will summa ize he
high- acuum he mal annealing p ocedu es ollowed in his hesis o ob ain pu i ied and
c ys alline 3D Co magne ic nanowi es om FEBID deposi s, main aining he o iginal
shape. In he case o 3D Fe-FEBID nanos uc u es, he e olu ion o he mo phology and
composi ional dis ibu ion was moni o ed in eal ime [31][46]. Such success ul pos -
p ocessing me hods may acili a e he de elopmen o u u e applica ions based on 3D
magne ic nanos uc u es.
4.2 Annealing p ocess on 3D cobal nanowi es
In his sec ion, he a en ion is d awn o he syn hesis o pu e and ully-c ys alline
3D Co nanowi es. The aim is o inc ease he c ys allini y and me allic con en unde ex
si u annealing, simul aneously imp o ing he sa u a ion magne iza ion alue. Mo eo e ,
ano he key objec i e is o minimize he olume sh inkage, ensu ing good mechanical
Towa ds p ope ies imp o emen by he mal annealing
149
s abili y o he 3D objec s. Thanks o he pu i ica ion p ocesses, he a en ion o as-g own
FEBID magne ic nanos uc u es can be ocused on ailo ing he la e al dimensions and
inc easing a chi ec u al accu acy o p oduce indi idual o a ays o cus omized 3D
nanos uc u es. These can be la e ex si u annealed o ob ain de ices o pu e ma e ial wi h
op imum magne ic esponse o he nume ous applica ions o eseen, i.e., magne ic da a
s o age and logic sys ems, Hall-e ec nanosensing, ca aly ic g ow h o nanos uc u es,
can ile e unc ionaliza ion o magne ic nanoac ua o s [38].
4.2.1 Expe imen al de ails
The nanos uc u es we e g own in he comme cial Helios Nanolab 650 Dual Beam
sys em using Co
2
(CO)
8
as p ecu so gas. A e he op imiza ion o he pa ame e s, he
deposi s we e ab ica ed selec ing an elec on beam ol age o 5 kV, an elec on beam
cu en o 100 pA and a chambe g ow h p essu e o 2.6 × 10
-6
mba (base p essu e o
1.3 × 10
-6
mba ). Two di e en ba ches we e g own unde he same main condi ions:
ba ch 1 o s uc u al, chemical and magne ic cha ac e iza ion, and ba ch 2 o
nanoSQUID magne ome y. In ba ch 1, he g ow h pa e n was a single poin scanned in
spo mode by he elec on beam o 45 seconds in s anda d TEM Cu g ids [31][39],
whe eas in ba ch 2 he g ow h was pe o med o 40-60 seconds on o a 500-nm- hick
Si
3
N
4
memb ane co e ed by 10 nm o Al a oiding cha ging e ec s o he nanowi e
which was no annealed and in hinned ( ew µm- hick) TEM Cu g ids o he nanowi es
de o ed o annealing [47].
The ex si u pos -g ow h annealing in high acuum ook place in an SEM Quan a
FEG 250 sys em. The SEM chambe was ini ially e acua ed un il he base p essu e
dec eased below 4 × 10
-6
mba . A hea ing amp o 50 ºC/min was p og ammed,
co esponding o he maximum allowed by he equipmen , un il he a ge annealing
empe a u e o each sample was eached. Then he samples we e annealed a 150 ºC,
300 ºC, 450 ºC and 600 ºC o 100 minu es. The use o me allic g ids is pa amoun o
Chap e 6
252
Figu e 6.10. Compa ison o he MFM images acqui ed in ai and wa e en i onmen s o he
comme cial Nanosenso s PP-MFMR and Team Nano ec ips, and o he unc ionalized
Olympus BioLe e mini wi h an Fe-FEBID nanowi e.
Gi en he pe o mance cons ain s o he comme cial p obes, expe imen s wi h
FEBID unc ionalized ips we e pe o med using dedica ed can ile e s o wo king in
liquid media. In pa icula , he Olympus BioLe e mini AFM p obe wi h a FEBID
nanowi e ensu es e y good pe o mance, as shown in Figu e 6.10 and 6.11, e idencing
ema kable imp o emen o con as wi h espec o he s anda d comme cial MFM ips
in liquid. In ac , he image quali y and sensibili y a e app oxima ely he same in bo h ai
and wa e . Also, his ip has shown an excellen pe o mance a e one yea in s o age.

Cu en and u u e applica ions based on FEBID
253
Figu e 6.11. MFM signal p o iles ob ained om he g een lines depic ed in Figu e 6.10 o
each ip case.
The FEBID ips allow selec ing he mos app op ia e can ile e o op imize he
MFM acquisi ion, a oiding he lack o adhesion o he magne ic laye o he p obe when
wo king in liquid media, con olling he s ay ield and ab ica ing deposi s wi h high
magne ic induc ion, which is impossible using he ypical spu e ing o e apo a ion
me hods due o he can ile e geome y. Addi ionally, an inc ease o he signal- o-noise
a io can be accomplished by minimizing he an de Waals in e ac ion hanks o a close
app oach o he FEBID ip o he sample han he comme cial ones. So a , he e is no
magne ic comme cial p obe which sa is ies hese equi emen s.
Chap e 6
254
6.1.5 Magne ic sky mions obse a ion
The magne ic sky mions a e spin ex u es o nanome ic scale which p esen
ou s anding po en ial p ope ies o spin onic applica ions. These opologically-
p o ec ed quasipa icles we e p edic ed heo e ically in he 1960s [21] and a e ypically
s abilized in sys ems p esen ing Dzyaloshinskii-Mo iya in e ac ion (DMI) and uniaxial
magne ic aniso opy [22][23][24][25]. The esul ing Bloch and Néel sky mions can be
ound in bulk non-cen osymme ic ma e ials [26] o ul a hin ilms wi h s ong spin-
o bi coupling in he in e ace [27][28][29].
To da e, he s abiliza ion o ei he Bloch o Néel sky mions was limi ed o sys ems
wi h in insic magne ic aniso opy. Howe e , an in es iga ion conduc ed in collabo a ion
wi h he g oup o D . Agus ina Asenjo p o ides an e idence o he s abiliza ion o Néel
sky mions in con ined sys ems wi h nei he DMI no pe pendicula magne ic aniso opy.
In pa icula , he de ec ion o he non-chi al magne ic Néel hedgehog sky mions was
pe o med a oom empe a u e in so magne ic sub-100 nm diame e polyc ys alline
nanodo s made o pe malloy whe e, howe e , ei he a o ex o a single domain s a e
wi h IP magne iza ion was expec ed due o low magne oc ys alline aniso opy [30][31].
The pe malloy nanodo s ha e p o en o se e as a chi ec u es o o m me as able
magne ic Néel sky mions, consis ing o o a ing he ou -o plane (OOP) magne iza ion
componen om he co e o he bounda ies by he spin cu ling in adial planes [32][33].
This has been demons a ed by analy ical calcula ions, mic omagne ic simula ions and
expe imen s based on applying ex e nal magne ic ields while pe o ming MFM
measu emen s [11].
Despi e his ema kable esul , he aim o his subsec ion is no o p esen a
comp ehensi e s udy o he hedgehog sky mions, bu o in oduce a no el po en ial in he
pe o mance o FEBID MFM ips. A g ea emphasis is o be gi en in he de ec ion,
obse a ion and s abiliza ion o he sky mions con igu a ion by he magne ic ield a isen
om hese unc ionalized ips.
Cu en and u u e applica ions based on FEBID
255
Whe eas in pe malloy nanodisks wi h 140 nm in diame e MFM images e eal da k
(a ac i e in e ac ion) o b igh ( epulsi e in e ac ion) con as a he cen e,
co esponding o he magne iza ion pa allel o an ipa allel o he ip pola iza ion; in sub-
100 nm nanodo s he con as is always b igh , e idencing an an ipa allel ip-co e
con igu a ion ega dless o he MFM ip pola iza ion, as illus a ed in Figu e 6.12(a). In
a sys em wi h diame e s below 30 nm, a non-sky mionic beha iou is exhibi ed,
es ablishing a adius bounda y o he sky mions s abiliza ion.
On he o he hand, as shown in Figu e 6.13, unde IP applied magne ic ield he
sky mions co e mo es pa allel o an ipa allel o he ield un il eaching a c i ical alue
when he magne iza ion is comple ely aligned wi h he ield di ec ion. These expe imen s
p o ed he exis ence o a adial IP magne iza ion componen in he nanodo s, disca ding
he o ex sys em and s ongly demons a ing he Néel sky mionic con igu a ion. In
addi ion, analy ical calcula ions sugges ha Néel sky mions a e highly me as able s a es
which can be s abilized in pe malloy nanodo s in absence o ex e nal ields and des oyed
by small pe u ba ions. In o de o e alua e he s abiliza ion o his singula
nanos uc u es conside ing he ip-sample in e ac ion, MFM expe imen s wi h di e en
ypes o p obe ha e been ca ied ou as a unc ion o he IP applied magne ic ield.
Figu e 6.12. MFM images pe o med wi h an Fe-FEBID ip o (a) nanodo s wi h 70 nm in
diame e p esen ing 100% o sky mion con igu a ion and (b) nanodo s wi h 30 nm in diame e
p esen ing 22% o sky mion con igu a ion, he es being single domain and o he di e en
con igu a ions.
Chap e 6
256
The expe imen al esul s a e displayed in Figu e 6.13, ce i ying ha he s ay ield
coming om he MFM ip con ibu es o he s abiliza ion o he sky mions [34]. The
comme cial Nanosenso s p obe p esen s he highes s ay ield, he Co-coa ed ip by
spu e ing o e s an in e media e alue and he Fe-FEBID nanowi e ip exhibi s he
lowes one. As can be no ed, he sa u a ing ield dec eases as he s ay ield p oduced is
educed. As a esul , he s ay ield o he ip enables he con ol o he sky mion s abili y.
In he la e case, a nanowi e o 1 µm in leng h, 30 nm in diame e and a e y sha p
apex wi h jus 7 nm allows imaging he sky mions wi h be e esolu ion and unde he
lowes ex e nal ip in asi eness, maximizing he OOP/IP s ay ield a io. Since he
applica ion o OOP s ay ields se es o une he s abili y o he sky mions, FEBID
nanoli hog aphy echnique can modula e he s abiliza ion p o iding he s ay ield
cus omiza ion. The e o e, he use o FEBID unc ionalized p obes un eils a new abili y
o analyse magne ic sky mions wi hou pe u ba ing hei magne ic s a e and explo ing
hei magne iza ion dynamics. Mo eo e , hese ips a e e y use ul o s udy magne ic
ex u es which a e e y much sensi i e o ex e nal pe u ba ions.
Figu e 6.13. MFM images pe o med wi h a comme cial Nanosenso s p obe, a Co-coa ed ip
and an Fe-FEBID nanowi e ip. The ield sequences show di e en IP ields depending on
he ype o ip. All image sizes a e 250
×
250 nm
2
.
Cu en and u u e applica ions based on FEBID
257
6.2 Enginee ed 3D cobal nanowi es
Shape cus omiza ion by FEBID en ails a g ea ad an age o he ab ica ion o 3D
samples wi h se e al ea u es. Apa om he s aigh s uc u al shape, his echnical
bene i enables a wide ange o a chi ec u al con igu a ions despi e i s di icul y. In his
sec ion, his asse will be u he exploi ed o g ow and in es iga e cu ed e omagne ic
FEBID nanos uc u es, pu suing he de elopmen o de ices based on he domain wall
mo ion such as high-densi y non- ola ile memo ies.
6.2.1 In oduc ion
Al hough a la ge a ie y o shapes and ma e ials can be p oduced by dis inc
echniques [35][36][37][38], he a chi ec u e o he nano-objec s is usually es ic ed o
s aigh cylind ical o ubula designs [39][40]. The possibili y o ab ica e 3D
nanos uc u es wi h many di e en geome ies by FEBID o e s a g ea e sa ili y in
e ms o shape, a eal densi y and no el magne ic domain con igu a ions [41]. Based on
hese undamen s and ha nessing he poly alence o his single-s ep nanoli hog aphy
echnology, enginee ed 3D Co and Co@P nanowi es ha e been designed con aining ben
segmen s which can p omo e he o ma ion o magne ic domain walls.
The s a egy o cu ed nanos uc u es seems easonable and well-adap ed o he
objec i e because he pinning o domain walls hanks o bending sec ions has al eady
been epo ed in expe imen al [42] and heo e ical [43] s udies, whe e an inc ease in
pinning si ua ions was de ec ed wi h he cu a u e and he angle o he bends [44][45].
The ollowing s udy aims o g ow 3D e omagne ic nanowi es wi h single o mul iple
e y well-de ined bends ac ing as pinning si es along he leng h o he nanos uc u e. The
magne ic s a e will be cha ac e ized explo ing he capabili y o such singula shapes o
gene a e speci ic si es whe e magne ic domains poin ing in di e en di ec ions mee o
o m a domain wall. As shown in Figu e 6.14, he pu pose o his geome y is o igge
he p esence o domain walls a emanence a e sa u a ing he sample wi h a magne ic

Chap e 6
258
ield applied pa allel o he subs a e and in he plane o he bends. Al hough his app oach
was es ed in he pas in many di e en sys ems, e.g., 2D cylind ical cu ed pe malloy
nanowi es [46], i s applica ion in 3D nano-objec s s ill cons i u es a majo challenge.
Rega ding he de ec ion o such magne ic con igu a ions, no con en ional magne o-
op ical and MFM me hods a e ully app op ia e o 3D s uc u es. Fo his eason, O -
Axis EH and X- ay magne ic ci cula dich oism in combina ion wi h pho oemission
elec on mic oscopy (XMCD-PEEM) echniques ha e been selec ed [47][48][49][50]. In
ac , al hough p e ious s udies on 3D samples o di e se shapes we e al eady epo ed
using bo h echniques [51][52][53], shadow XCMD-PEEM had no been pe o med in
e ical nanos uc u es wi h such high aspec a io.
Figu e 6.14. SEM images o a 3D Co@P nanowi e (a) be o e and (b) a e he P -C coa ing.
(c) Scheme o he IP magne ic ield applica ion a ou ing he domain walls o ma ion a
emanence in he a eas indica ed by ed- immed ci cles, whe e he al e na ing magne ic
cha ge a e deno ed.
6.2.2 Expe imen al de ails
The nanos uc u es we e g own in he comme cial Helios Nanolab 650 Dual Beam
sys em using Co
2
(CO)
8
and CH
3
CpP (CH
3
)
3
p ecu so gases. The subs a es we e TEM
Cu g ids and Si wa e s. The Co nanowi es we e ab ica ed wi h a 5 kV elec on beam
ol age, a 100 pA elec on beam cu en and a chambe g ow h p essu e o 3.3 × 10
-5
Cu en and u u e applica ions based on FEBID
259
mba (base p essu e o ~4.7 × 10
-6
mba ). Al hough each segmen o he nanowi e could
be ab ica ed sepa a ely il ing he s age a e e y s age, he e he whole Co nanos uc u e
was g own in one single deposi ion wi h he s age emaining in he ho izon al posi ion.
The Co pa e n is composed o 77 poin s sepa a ed 14 nm in a s aigh line pa allel o he
la edge o he Co GIS, keeping cons an he p ecu so molecules lux gua an eeing no
shadowing e ec [54]. As illus a ed in Figu e 6.14, he nanowi e is o med by se en
segmen s —numbe ed om bo om o op—, each one ha ing i s pa icula g ow h
s a egy. Ve ical segmen s a e ob ained by scanning a single pa e n poin while he
elec on beam s ands s ill. By con as , ben segmen s a e ab ica ed by scanning a
sequence o 18 poin s while shi ing he elec on beam posi ion. Fo a ixed o al
ho izon al shi and dwell ime du ing he sequence, he angle o he segmen wi h espec
o he subs a e depends on he numbe o poin s. The highe ha numbe , he sho e he
dis ance be ween wo subsequen poin s, and he e o e he o e lap be ween hem will be
highe and he angle wi h espec o he subs a e will inc ease. Each ben segmen
co esponds o 18 pa e n poin s wi h a scanning ime o 97.2 ms. To o m he ∼90 deg ees
bends, he join be ween he ben segmen s is ab ica ed by a single poin scanned o
581.2 ms. Then, he bend is comple ed by e e sing he elec on beam shi di ec ion.
The i s segmen was g own by deposi ing on he i s poin o 2903.8 ms. Then,
he second and he hi d ones we e ab ica ed scanning he sequence o 18 poin s o each
one, as desc ibed abo e, aking in o accoun ha he poin s o he hi d one a e exac ly
o e hose o he second segmen bu scanned in he e e se di ec ion, hus o ming he
i s bend o he nanos uc u e. The ou h segmen was comple ed scanning a single poin
o 1549.1 ms. Then, he i h and he six h segmen s, as well as he join be ween hem
we e ca ied ou jus as he i s bend. The op segmen was ab ica ed scanning he las
poin du ing 2419.8 ms. On he o he hand, ollowing he same p ocedu e, 3D Co
nanowi es wi h only one bend ha e also been ab ica ed.
Chap e 6
260
Fo he Co@P nanowi es, he P -C shell was g own immedia ely a e he
e omagne ic co e (~65%–70% a . Co) ollowing he p ocess desc ibed in Chap e 5 in
o de o a oid i s oxida ion [22]. An elec on beam ol age o 5 kV and an elec on beam
cu en o 100 pA we e used, wi h a chambe g ow h p essu e o 2.4 × 10
-5
mba . In his
case, a polygonal P -C pa e n was se ollowing he shape o he nanowi e co e iewed
om he pe spec i e shown in Figu e 6.14(a). A P -C deposi ion o ~2 s in each side
inc eases he diame e by ~13 nm, as seen in Figu e 6.14(b).
In o de o cha ac e ize magne ically he e omagne ic nanowi es, O -Axis EH and
XMCD-PEEM imaging expe imen s ha e been pe o med. In he i s one, expe imen s
we e pe o med in he FEI Ti an Cube, ope a ed a 300 kV. The exci a ion o he bip ism
was adjus ed acco ding o he nanowi es shape, wi h a inge con as anging om 20%
o 25% and an acquisi ion ime o 5 s. The second echnique was ca ied ou in he
XPEEM b anch o he HERMES beamline (Synch o on SOLEIL-F ance) [35] by he
g oup o D . Oli ie F ucha .
6.2.3 Magne ic s a e cha ac e iza ion
Fi s ly, O -Axis EH expe imen s we e pe o med on single-bend 3D Co nanowi es
o check he pinning o domain walls a emanence in he bends a e applying a magne ic
ield in he app op ia e di ec ion, i.e., in he plane o he bends and app oxima ely
pe pendicula o he subs a e su ace. As illus a ed in Figu e 6.15, wo almos iden ical
nanos uc u es we e used o explo e he ep oducibili y o he expe imen . The esul s
show ha wo di e en domain walls we e ound in he i s and second bends s a ing
om he bo om, which is e idenced by he con as change o he magne ic lux lines in
he bend and he p esence o s ay ields in he su ounding acuum. In ac , he wo
domain walls can be app ecia ed in he same places in each nanowi e, gua an eeing he
eplicabili y o i s o ma ion.
Cu en and u u e applica ions based on FEBID
261
Figu e 6.15. (a,c) SEM images o wo di e en 3D Co nanowi es and (b,d) hei associa ed
magne ic lux lines dis ibu ion.
In XMCD-PEEM expe imen s, he shadow o he nanos uc u e gene a ed when he
beam passes h ough he specimen p o ides in o ma ion o eco e ing he magne ic
con igu a ion o he sample. On he one hand, he magne ic imaging wi h synch o on
so X- ays is based on he magne ic ci cula dich oism, e ealing he di e ence in
esonan abso p ion o le and igh ci cula ly-pola ized ligh and ob aining he
p ojec ion o he magne iza ion. On he o he hand, he collec ion o pho oelec ons
coming om he nanos uc u e du ing X- ay abso p ion allows imaging. Speci ically, he
image con as , which is p opo ional o he cosine o he angle be ween he beam wa e
ec o and he magne iza ion di ec ion, is used o he econs uc ion o he magne ic
con igu a ion.
As al eady sugges ed in Figu e 6.14, a e applying he magne ic ield —pa allel o
he subs a e and in he bends plane—, h ee domain walls a e expec ed o be nuclea ed
on double-bend 3D Co nanowi es. Figu e 6.16 shows he co ela ion be ween he shadow
ea u es and he magne ic s a e o he segmen s. Whe eas he s ong ield emission a he
nanowi e ip leads o a educ ion o he signal- o-noise a io, he op segmen s (4, 5 and
7) a e clea ly iden i ied in Figu e 6.16(b), a away om he nanowi e posi ion. The lack
Chap e 6
268
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Chap e 7: Gene al conclusions and
ou look
In his chap e , a global o e iew o he key esul s p esen ed in his hesis and he
main conclusions emana ed om hem a e p esen ed, oge he wi h he p omising
p ospec s o he u u e esea ch on 3D FEBID magne ic nanos uc u es in he amewo k
o Nanomagne ism.
Chap e 7
270
Since he eme gence o Nano echnology and he mul i ude o applica ions de i ed
om i , in ensi e e o s ha e been de o ed o ab ica ing unc ional nanos uc u es.
Speci ically, magne ic nanos uc u ed ma e ials a ac pa icula ly keen in e es because
o hei would-be implemen a ion in key in o ma ion and communica ions echnologies,
such as da a s o age, logic and sensing de ices [1]. Acco dingly, he de elopmen o
no el nano ab ica ion echniques o he e inemen o he exis ing me hods is one o he
essen ial co ne s ones o he g ow h o ad anced nano-objec s, allowing he subsequen
s udy o physical phenomena a nanome ic scale [2].
In his ligh , Focused Elec on Beam Induced Deposi ion (FEBID) a ises as one o
he mos e sa ile nano ab ica ion echnologies which could play a c ucial ole in he
p oduc ion o se e al ypes o a chi ec u es and ma e ials in he nanoscale [3]. Du ing he
las decades, his single-s ep li hog aphic me hod has been widely used o he g ow h o
wo-dimensional deposi s, c ea ing magne ic nanos uc u es conside ed as p omising
candida es o he de elopmen o o hcoming spin onic applica ions. Howe e , he
inc easing demand o high-densi y and low-powe nanode ices na u ally en ails he
expansion o h ee-dimensional (3D) deposi s [4]. As a esul , e ical magne ic
nanos uc u es a e cu en ly a cen al opic in nanomagne ism. The unc ionali y o hese
po en ial building blocks o 3D magne ic de ices elies on he p ecise con ol o domain
wall mo ion wi h spin-pola ized cu en s o magne ic ields which, combined wi h he
high a eal densi y allowed by 3D a chi ec u es, is bound o boos hei ope a ional
pe o mance.
The o e a ching objec i e o his hesis in ol es he syn hesis and cha ac e iza ion
o 3D e omagne ic nanowi es, in ending o shed ligh upon no el and ad anced
op imiza ion p ocesses which help o imp o e he ope a ional beha iou o hese
nanos uc u es. The main achie emen s p esen ed in his manusc ip a e desc ibed below.
Gene al conclusions and ou look
271
7.1 Tailo ing o 3D nanowi es g own by FEBID
Fi s ly, he FEBID e sa ili y has been exploi ed o adjus he hickness, composi ion
and magne ic induc ion o 3D Co nanowi es. In his ega d, nanos uc u es wi h double-
sec ion diame e s, di e en shapes and chemical con en s ha e been in es iga ed,
p o iding insigh on he linea and adial g ow h egimes. The in e p e a ion o he esul s
indica es ha he mal and di usion e ec s a e ul ima ely esponsible o hese g ow h
modes, helping in he p og ess owa ds u u e upg aded nano ab ica ion s a egies. As a
p ac ical example, diame e changes o ben shapes a e na u al loca ions o magne ic
domain-wall pinning wi h applica ions in magne ic s o age and logics.
S anding by hese a gumen s, simul aneous high me allic con en (~80% a .), small
diame e s (<100 nm) and high magne ic induc ion (~1 T) ha e been ob ained o
nanowi es g own unde op imized condi ions. These esul s a e a o wa d s ep o he goal
o d i ing FEBID owa ds a ema kably p ac ical nanoli hog aphy echnique o ab ica e
3D unc ional nanos uc u es wi h unique la e al esolu ion. Along his line, Co and Fe
nanowi es wi h e y sha p apex ha e been analysed and ound o be ideal a chi ec u es
o Magne ic Fo ce Mic oscopy measu emen s.
Secondly, he di icul y o FEBID o ab ica e nanos uc u es on insula ing
subs a es due o se e e cha ging e ec s has been o e come by using he ARchi ec u al
Adjus men by G id O e lay Nano echnology (ARAGON) Chip, an elec ically-biased
pa e ned me al s uc u e which enables cha ge e acua ion du ing he g ow h o nano-
objec s. In addi ion, his no el app oach has been p o en o se e as a new knob o in
si u modula ion o he nanowi e geome y, by din o he applica ion o spa ially-
dependen elec ic ields, ac ing as an elec os a ic lens on he ajec o ies o he p ima y
and seconda y elec ons. The e o e, he in si u modi ica ion o he applied ol age o he
ocus heigh o e s a new ou e o c ea e 3D unc ional complex nanos uc u es wi h
ailo ed la e al dimensions. These indings ha e enabled no only a be e unde s anding
o he g ow h mechanisms by FEBID, bu also hin ing new app oaches o he
Chap e 7
272
implemen a ion o he ARAGON-Chip. Fo ins ance, ins ead o pa e ning he holed
me al pla e on o he sample, he ARAGON-Chip could be edesigned o be inse ed
au oma ically in he icini y o he subs a e as an ape u e in he Scanning Elec on
Mic oscopes, wi h di e en hole geome ies o p oduce cus om dis ibu ions o elec ic
ields.
7.2 Annealing ea men s o op imize nanowi e p ope ies
The c ys allini y, composi ion and magne ic induc ion o 3D e omagne ic Co and
Fe nanowi es di e s g ea ly om he bulk ma e ials mainly due o he p esence o
impu i ies coming om he incomple ely dissocia ion o he p ecu so gas molecules. In
o de o emo e hese undesi ed byp oduc s, pos -g ow h high- acuum annealing
p ocesses ha e been pe o med.
In he case o Co, ex si u he mal annealing a 600 ºC has been ound o p oduce
pu i ied and c ys alline nanowi es wi h diame e s below 90 nm, a me allic con en abo e
95% a ., and a ne magne ic induc ion up o 1.6 T, nea he bulk Co. The combined e ec
o con aminan s mig a ion o he su ace and ec ys alliza ion o he as-g own
nanoc ys alline s uc u e gi es ise o nanowi es wi h physical p ope ies close o bulk
ones. Besides, gi en he ela i ely high me al con en o he as-g own deposi s (~70%
a .), he changes in shape o he deposi s a e pu i ica ion is minimal, acili a ing hei
unc ional implemen a ion in 3D de ices.
In he case o Fe, eal- ime moni o ing o he chemical pu i ica ion and s uc u al
c ys alliza ion p ocesses o ul a-na ow nanowi es (<50 nm in diame e ) has been ca ied
ou by in si u annealing in a T ansmission Elec on Mic oscope. The hea ing up o 700 ºC
e eals local inc eases o he me allic con en along he nanowi e leng h concomi an
wi h he g ow h o la ge Fe single c ys als om ini ially pseudo-amo phous compounds
wi h jus ~40% a . o Fe. Besides, a educ ion o he diame e down o ~30 nm has been
achie ed in he highes me allic egions. This e olu ion acking has p o ided insigh in o
Gene al conclusions and ou look
273
he nanoscale p ocesses in ol ed du ing he annealing ea men , se ing as a u u e ideal
me hod o de e mining he minimum equi emen s o pu i y and geome y o as-g own
nanowi es and he app op ia e he mal condi ions o be success ully annealed.
Along
his
line o hough , u u e ad ances in he pu i ica ion s a egies could poin owa ds
explo ing u he c ys alliza ion upon longe and p ecise annealing imes wi h he aim o
ou inely p oducing high-quali y single-c ys alline nanowi es o he use o eac i e
a mosphe e o e ch he emaining con aminan s a he su ace [5]. The same ou e could
be used o explo e he possibili y o annealing bime allic o he e ogeneous sys ems and
he po en ial o empe a u e-induced alloying.
7.3 Dual pu pose o he co e-shell a chi ec u al app oach
On he one hand, he na u al su ace oxida ion o he e omagne ic nanos uc u es
o a non- e omagne ic ma e ial (~5 nm in hickness) implies he deg ada ion o he
magne ic p ope ies o 3D Co and Fe nanowi es, which becomes c i ical a he smalles
diame e s. This nega i e impac can be pallia ed by g owing a 10-20 nm- hick P -C
p o ec i e shell, e aining he o iginal ne magne ic induc ion. This imp o emen wi h
espec o he uncoa ed nanowi es can each 35% o he hinnes nanowi es (<40 nm co e
diame e s), when he su ace oxidized laye g ea ly con ibu es o he o al nanowi e
diame e . This s a egy demons a es ha he ope abili y o nanos uc u ed objec s o en
elies on he combina ion o mo e han one ma e ial, enhancing he pe o mance o he
de ice o con e ing he desi ed unc ionali y.
On he o he hand, 3D ul a- hin Co nano ubes ha e also been syn hesized on P -C
empla es adap ing he co e-shell app oach o p oduce P @Co nanowi es. Dimensional,
composi ional and magne ic cha ac e iza ion has p o ed he e omagne ic beha io o
he Co nano ubes and allowed s udying hei magne iza ion s a e and dynamics. The
swi ching mechanism is go e ned by he domain-wall o ma ion and p opaga ion, ha ing
a s ong and po en ial impac in he unc ionali y o de ices composed by hese

Chap e 7
274
nanos uc u es. In pa icula , e omagne ic nano ubes a e o emendous in e es o
in es iga ions o as -p opaga ing magne ic domain walls, which is a oo-demanding
equi emen o he de elopmen o applica ions wi hin Nanomagne ism.
Re e ences
[1] S. S. P. Pa kin, M. Hayashi and L. Thomas, “Magne ic domain-wall ace ack
memo y”, Science 320, 190 (2008).
[2] M. Vázquez, “Magne ic Nano- and Mic owi es. Design, Syn hesis, P ope ies and
Applica ions”, Else ie (2015).
[3] M. Hu h, F. Po a i, C. Schwalb, M. Winhold, R. Sachse , M. Dukic, J. Adams
and G. Fan ne , “Focused elec on beam induced deposi ion: A pe spec i e”,
Beils ein J. Nano echnol. 3, 597 (2012).
[4] A. Fe nández-Pacheco, R. S eubel, O. F ucha , R. He el, P. Fische and R. P.
Cowbu n, “Th ee-dimensional nanomagne ism”, Na . Commun. 8, 15756 (2017).
[5] E. Begun, O. V Dob o olskiy, M. Kompaniie s, R. Sachse , C. Gspan, H. Plank
and M. Hu h, “Pos -g ow h pu i ica ion o Co nanos uc u es p epa ed by ocused
elec on beam induced deposi ion”, Nano echnology 26, 075301 (2015).
Conclusiones gene ales y pe spec i as
275
Conclusiones gene ales y pe spec i as
En es e capí ulo se p esen a un esumen de los p incipales esul ados ob enidos e
incluidos en es e documen o. Asimismo, de o ma global se ecogen las conclusiones
gene ales su gidas de es a esis doc o al, acompañadas de unas pe spec i as
p ome edo as y con g an po encial pa a u u as in es igaciones con es uc u as 3D
ab icadas po deposición inducida po haz ocalizado de elec ones den o del ma co del
Nanomagne ismo.
Chap e 7
276
Desde el su gimien o de la Nano ecnología y de las múl iples aplicaciones de i adas
de es e campo, se han dedicado nume osos es ue zos pa a la ab icación de
nanoes uc u as uncionales. Especí icamen e, los ma e iales magné icos
nanoes uc u ados a aen un g an in e és po sus po enciales implemen aciones en
ecnologías de la in o mación y la comunicación, ales como los disposi i os dedicados
al almacenamien o, lógica y de ección magné icos [1]. En es e sen ido, el desa ollo de
nue as écnicas de nano ab icación o el pe eccionamien o de los mé odos ya exis en es
es una de las pied as angula es pa a el c ecimien o de nano-obje os a anzados,
pe mi iendo el consiguien e es udio de los enómenos ísicos a escala nanomé ica [2].
En es e con ex o, la deposición inducida po haz ocalizado de elec ones (FEBID)
su ge como una de las écnicas de nano ab icación más e sá iles, la cual puede
desa olla un papel c ucial en la p oducción de es uc u as con di e sas o mas y
ma e iales en la nanoescala [3]. Du an e las úl imas décadas, es e mé odo de
nanoli og a ía se ha u ilizado ampliamen e pa a el c ecimien o de depósi os en dos
dimensiones, c eando nanoes uc u as magné icas conside adas como candida as
po enciales pa a el desa ollo de los u u os disposi i os espin ónicos. Sin emba go, la
c ecien e demanda pa a gene a mé odos de almacenamien o de in o mación en
nanodisposi i os de al a densidad y con meno consumo de ene gía conlle a de o ma
na u al a in es iga depósi os en es dimensiones (3D) [4]. Como esul ado, las
nanoes uc u as magné icas e icales se e igen ac ualmen e como unos de los emas
cen ales den o del Nanomagne ismo. La uncionalidad de es as piezas básicas pa a los
u u os disposi i os magné icos en 3D ecae en la posibilidad de con ola de o ma
p ecisa el mo imien o de las pa edes de dominio, bajo la aplicación de co ien es de espín
pola izadas o de campos magné icos que, combinados con la mayo densidad de á ea
o ecida po las es uc u as 3D, pe mi e aumen a su endimien o [2].
El obje i o p incipal de es a esis doc o al in eg a la sín esis y ca ac e ización de
nanohilos e omagné icos en 3D, a ando de a oja luz sob e nue os y a anzados
Conclusiones gene ales y pe spec i as
277
p ocesos de op imización que ayuden a mejo a el compo amien o ope acional de es as
nanoes uc u as. A con inuación, se desc iben los p incipales esul ados p esen ados en
es e documen o.
7.1 Diseño de nanohilos 3D c ecidos po FEBID
En p ime luga , la e sa ilidad de la écnica FEBID ha sido ap o echada pa a el
ajus e del espeso , composición e inducción magné ica de nanohilos de Co en 3D. En es e
sen ido, se han in es igado nanoes uc u as de diáme o a iable, con di e en es o mas
y con enido me álico, p opo cionando un conocimien o y comp ensión más p o undos
sob e los egímenes de c ecimien o lineal y adial. La in e p e ación de los esul ados
indica que los e ec os é micos y de di usión son los esponsables de los di e en es modos
de c ecimien o en úl imo é mino, suponiendo un impulso pa a la mejo a y ac ualización
de las u u as es a egias de c ecimien o median e es a écnica. Como ejemplo p ác ico,
cabe des aca que las egiones donde se modi ica el diáme o son si ios na u ales de
anclaje pa a las pa edes de dominio, con aplicaciones en almacenamien o y lógica
magné icos.
En base a es os a gumen os, bajo condiciones op imizadas, se han ob enido
nanohilos con al o con enido me álico (~80% a .), educido diáme o (<100 nm) y al os
alo es de inducción magné ica (~1 T). Es os esul ados suponen un paso adelan e pa a
el obje i o de si ua a la écnica FEBID como un mé odo de li og a ía ex ao dina io pa a
la ab icación de nanoes uc u as uncionales en 3D con esoluciones la e ales únicas. En
es a línea, se ha comp obado que nanohilos de Co y Fe con pun as muy a iladas son
es uc u as ideales pa a medidas en Mic oscopía de Fue za Magné ica.
En segundo luga , la di icul ad de la écnica FEBID pa a la ab icación de
nanoes uc u as sob e sus a os aislan es debido a los se e os e ec os de ca ga, ha sido
encida median e el uso del ARchi ec u al Adjus men by G id O e lay Nano echnology
(ARAGON) Chip, es deci , un chip o mado po una es uc u a me álica con o ma de
Annex A
284
Figu e A.1. Examples o elec on holog ams o di e en 3D Co nanowi es: (a) as-deposi ed
and annealed a (b) 150 ºC, (c) 300 ºC, (d) 450 ºC and (e) 600 ºC.
Whe eas bo h holog ams include he same elec os a ic phase shi con ibu ion, he
magne ic con ibu ion changes i s sign. A e he addi ion and sub ac ion o he
holog ams, he wo solu ions ob ained always cancelled one o he phase con ibu ions
gi ing ise o an image wi h wo imes he o he one. As a esul , he elec os a ic and
magne ic phase shi images can be plo ed sepa a ely, as shown in Figu e A.2.
The g adien o he phase shi can be calcula ed as:
∇



,


=
∇




,


+
∇




,


=
(A.2)
_
_
_
_
_
_
_
_
_
_

=







,


−

ℏ




,





,


whe e 

=  
∗
⁄ is a cons an which depends on he ene gy o he inciden elec on
beam wi h a alue o 

= 6.53 × 10
6
ad·V
-1
·m
-1
a 300 kV, 

is he mean inne
po en ial and has a alue o 26 V o pu e Co [7] and 17.4 V o Fe [8], is he magne ic
hickness o he specimen, e is he elec on cha ge, ћ is he educed Planck cons an , x
and y a e o hogonal equi alen di ec ions in he plane o he sample and 

he magne ic
induc ion componen pe pendicula o one o he in-plane componen s and he elec on
beam di ec ion, z.

Elec on Holog aphy da a p ocessing
285
Figu e A.2. (a) Elec os a ic and (b) magne ic phase shi images ex ac ed om a 3D Co
nanowi e. (c) P o iles o bo h ypes o phase shi s along he g een a ows a e aged ac oss a
leng h o 58 nm.
Since he nanos uc u es a e no usually composed by a pu e ma e ial, 

alue
does no co espond o ha o he bulk. Thus, conside ing he i s e m o he igh -hand
side o Equa ion A.2, he elec os a ic phase shi image can be used o calcula e 

,
knowing 

alue and he nanowi e hickness, assuming ha he nano-objec is
cylind ical and chemically homogeneous. Then, a ending o he second e m o he igh -
hand side o Equa ion A.2, he magne ic induc ion can be calcula ed by s aigh o wa d
Annex A
286
ma hema ical ope a ions using he g adien o he magne ic phase shi image conside ing
one o he wo equi alen di ec ions, x and y. Fo ins ance, in he case o he x axis:
|




,


|
=
ℏ

·

#




,


#
(A.3)
Figu e A.2 simul aneously demons a es he cylind ical shape o he nanos uc u e
(

p o ile) and shows he change o he 

which p o es he e omagne ic
beha io o he nanowi e. Indeed, he s eepe he slope, he highe he magne ic induc ion.
Finally, he magne ic lux ep esen a ion can be illus a ed no malizing he magne ic
phase con ibu ion o he maximum hickness o a be e compa ison and calcula ing he
cosine o n imes he magne ic phase shi .
Figu e A.3. Magne ic induc ion lux ep esen a ions o di e en 3D Co nanowi es: (a) as-
deposi ed and annealed a (b) 150 ºC, (c) 300 ºC, (d) 450 ºC and (e) 600 ºC.
Re e ences
[1] M. J. Hÿ ch, E. Snoeck and R. Kilaas, “Quan i a i e measu emen o displacemen
and s ain ields om HREM mic og aphs”, Ul amic oscopy 74, 131 (1998).
[2] L. A. Rod íguez, C. Magén, E. Snoeck, C. Ga el, L. Ma ín, L. Se ano-Ramón, J.
L. P ie o, M. Muñoz, P. A. Alga abel, L. Mo ellon, J. M. De Te esa and M. R.
Iba a, “Quan i a i e in si u magne iza ion e e sal s udies in Lo en z mic oscopy
and elec on holog aphy”, Ul amic oscopy 134, 144 (2013).
[3] H. Lich e and M. Lehmann, “Elec on holog aphy-basics and applica ions”, Rep.
P og. Phys. 71, 016102 (2008).
[4] A. Tonomu a, T. Ma suda, J. Endo, T. A ii and K. Mihama, “Holog aphic
in e e ence elec on mic oscopy o de e mining specimen magne ic s uc u e
and hickness dis ibu ion”, Phys. Re . B 34, 3397 (1986).
Elec on Holog aphy da a p ocessing
287
[5] J. C. Loudon, N. D. Ma hu and P. A. Midgley, “Cha ge-o de ed e omagne ic
phase in La
0.5
Ca
0.5
MnO
3
,” Na u e 420, 797 (2002).
[6] R. E. Dunin-Bo kowski, M. R. McCa ney, B. Ka dynal and D. J. Smi h,
“Magne ic in e ac ions wi hin pa e ned cobal nanos uc u es using o -axis
elec on holog aphy”, J. Appl. Phys. 84, 374 (1998).
[7] M. De G ae , N. T. Nuh e , and M. R. McCa ney, “Phase con as o sphe ical
magne ic pa icles”, J. Mic osc. 194, 84 (1999).
[8] T. Fuji a, M. Chen, X. Wang, B. Xu, K. Inoke and K. Yamamo o, “Elec on
holog aphy o single-c ys al i on nano ods encapsula ed in ca bon nano ubes”, J.
Appl. Phys., 101, 014323 (2007).
Annex B: Mechanical p ope ies o 3D
cobal nanowi es
B.1 In oduc ion
Nanowi es ha e also a high in e es because o hei po en ial applica ions in elec o-
mechanical de ices [1][2]. Al hough he mechanical cha ac e iza ion o hese
nanos uc u es is no s aigh o wa d, i is c i ically impo an o unde s and hei
pe o mance beha iou and de e mine hei mechanical p ope ies. Fo his pu pose, he
ab ica ion and cha ac e iza ion o suspended 3D Co nanowi es g own by FEBID ha e
been ca ied ou .
Se e al app oaches a e used o he mechanical analysis such as AFM
nanoinden a ion [3], con ac esonance AFM [4], AFM bending [5], in si u SEM
esonance [6] and ension [7] o in si u TEM esonance [8] and ension [9]. He e, he
h ee-poin bending me hod by AFM is p oposed [10][11], consis ing o he bending o a
double-clamped suspended nanos uc u e. On his basis, ho izon ally-suspended double-
clamped Co nanowi es ha e been syn hesized wi h diame e s be ween ~55 and ~75 nm
and a suspended leng h o 1.2 µm. Then, he Young modulus and he yield s eng h ha e
been in es iga ed.
B.2 Expe imen al de ails
The nanowi es we e ab ica ed in he comme cial Helios Nanolab 650 Dual Beam
sys em using Co
2
(CO)
8
as p ecu so gas. The subs a e consis s o a ays o mic o-
enches be ween Si pads sepa a ed 1.2 µm, pa e ned by op ical pho oli hog aphy and
eac i e ion e ching. The suspended nanowi es we e g own ac ing as a b idge be ween
he pads, as shown in Figu e B.1.

Annex B
290
The deposi s we e ab ica ed wi h an elec on beam ol age o 5 kV, an elec on
beam cu en o 100 pA and a chambe g ow h p essu e o ~2.3 × 10
-5
mba (base p essu e
o ~1.5 × 10
-6
mba ). The pa e n was o med by an a ay o 120 poin s, sepa a ed 15 nm
be ween each o he , connec ing wo Si pads. The elec on beam scanned only once om
one edge o he o he wi h a dwell ime o 1 µs. To compensa e he na u al inclina ion o
he nanowi e wi h espec o he ho izonal axis due o he o e lap o he poin s sequence,
he subs a e was il ed ~35-45 deg ees wi h espec o he ho izon al axis o make he
connec ion possible. EDS expe imen s a e he na u al oxida ion o he nanos uc u es
e ealed chemical composi ions o ~53% a . Co, ~20% a . C and ~27% a . O.
The mechanical cha ac e iza ion o he nanowi es was pe o med using a Dimension
ICON AFM om B uke . The bending es s we e ca ied ou applying a o ce in he
midpoin o he nanowi e and measu ing i s displacemen . The sp ing cons an s o he
can ile e s we e 3 and 20 N·m
-1
, wi h a ip app oaching speed om 100 o 500 nm·s
-1
.
Figu e B.1. Schema ic diag am illus a ing he FEBID p ocess o he ab ica ion o 3D
ho izon ally-suspended Co nanowi es. No ing ha du ing he p ocess he s age was il ed ~35-
45 deg ees wi h espec o he ho izon al posi ion. The inse shows an SEM image o a 3D
Co nanowi e.
Mechanical p ope ies o 3D cobal nanowi es
291
B.3 Resul s and discussion
The bending expe imen was pe o med wi h an AFM ip a he midpoin o he
nanowi e, unde aking a load-unload p ocess o ob ain he ela ionship be ween he
applied o ce and he displacemen o he cen al pa o he nanos uc u e. Figu e B.2(a)
shows he ypical cu e acqui ed below he ac u e load poin . The o e lap be ween he
load and unload da a e eals he absence o hys e esis. In addi ion, AFM and SEM
inspec ions pe o med a e hese bending expe imen s did no indica e any ailu e o he
clamping si es.
To de e mine he Young modulus, , and he yield s eng h, 

, he h ee-poin
bending me hod was ca ied ou un il he nanowi es ac u e. Figu e B.2(b) plo s he
mechanical beha iou o a Co nanowi e, whe e a linea end wi h pu e elas ic beha iou
can be iden i ied in he small de lec ion ange and ends o g ow when inc easing
de lec ions [12] be o e he ac u e, e idenced by a dec ease o he applied o ce.
Figu e B.2. (a) AFM image o a 3D Co nanowi e, ep esen ing he bending o ce as a unc ion
o he displacemen , whe e he load ( ed) and unload (blue) cu es a e shown. (b) Plo o he
bending expe imen whe e he linea egion and he ac u e a e highligh ed. The inse shows
an AFM image o he Co nanowi e a e he ac u e. Unde ined colou scale ange and scale
ba s in all images a e 100 and 200 nm, espec i ely.
Annex B
292
Fi s ly, om he linea egion, conside ing he appa en elas ic cons an , 

, i.e., he
slope o he expe imen al cu es,  can be calcula ed acco ding o he ollowing equa ion,
co esponding o a double-clamped nanowi e wi h diame e , , and suspended leng h, 
[13][14]:

=




3



(B.1)
whe e 

is calcula ed om he linea i o he bending cu es.
The expe imen al alue o  anges om (58
±
5) GPa o (209
±
24) GPa o
nanowi es be ween ~55 nm and ~75 nm in diame e , no icing a sligh associa ion o he
highe  alues wi h he smalle diame e s. Thus, hese esul shows ha he  alues o
he na owe nanowi es a e e y close o he bulk one (~209 GPa), and he alues
ob ained o he wide nanowi es a e compa able o he ones epo ed o polyc ys alline
Co oxide nanowi es [10].
Secondly, he subsequen non-linea beha iou is compa able o ha epo ed o
double-clamped Si [14], Au [15] and ZnO [16]. When he displacemen begins o no be
compa able o he nanowi e adius, he axial ension due o s e ching domina es o e he
adial one and he cu e depa s om he linea beha iou .
Thi dly, he applied o ce educ ion e idences he nanowi e’s plas ic de o ma ion
and, inally, he ac u e. Along his line, he yield s eng h, 

, de ined as he s ess a
which he ma e ial s a s o be de o med plas ically, can be es ima ed using he ollowing
exp ession [15]:


=
4






(B.2)
whe e 

is he yield o ce, co esponding o he maximum load immedia ely be o e he
ac u e. An a e age 

o (6.1
±
2.3) GPa was ound, no a om he heo e ical one
(

~0.1) [17], bu signi ican ly g ea e han he bulk Co alue (

~345-485 MPa).
Mechanical p ope ies o 3D cobal nanowi es
293
The ac u e occu s ypically by he eme gence o issu es o igina ed a de ec s [18].
Since he p obabili y o p oducing a issu e dec eases wi h educing he ma e ial size
[15], nanos uc u es a e expec ed o unde go highe s ess han bulk ma e ials. The e o e,
he highe 

alues ob ained o nanowi es can be explained by he limi ed numbe o
de ec s. Addi ionally, di e ences in he mic os uc u e and composi ion o he Co
nanowi es ab ica ed by FEBID wi h espec o he bulk can also con ibu e owa ds
imp o ing 

, e.g., no icing ha he small g ain sizes p esen in he nano-objec s hampe s
he o ma ion o de ec s.
Simila esul s ha e been ob ained by us on he mechanical p ope ies o suspended
W-C nanowi es g own by FIBID and in es iga ed using he same expe imen al echnique
[19].
B.4 Conclusions
A no el nano ab ica ion me hod o he g ow h o ho izon ally-suspended 3D Co
nanowi es by FEBID has been p esen ed. The mechanical cha ac e iza ion pe o med by
he h ee-poin bending me hod shows good mechanical pe o mance o he
nanos uc u es wi h Young modulus alues compa able o he bulk ma e ial ones, and
exhibi ing a yield s eng h 15 imes highe han he bulk one. The small la e al esolu ion
and he mic os uc u e o hese 3D nanos uc u es con e s he nanowi es ou s anding
mechanical p ope ies which p o ide obus ness, po en ially cons i u ing he basis o he
design o u u e ad anced nano-mechanical de ices.
Re e ences
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Nanowi e Elec omechanical Resona o s”, Nano Le . 7, 1953 (2007).
[2] P. Va asso i, M. Pancaldi, M. J. Pe ez-Roldan, A. Chu ilin and A. Be ge ,
“Remo e Magne omechanical Nanoac ua ion”, Small 12, 1013 (2016).
[3] X. Li, H. Gao, C. J. Mu phy and K. K. Caswell, “Nanoinden a ion o Sil e
Nanowi es”, Nano Le . 3, 1495 (2003).